/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */

module hunt.concurrency.ConcurrentHashMap;

import hunt.concurrency.ConcurrentMap;

// import java.io.ObjectStreamField;
// import java.io.Serializable;
// import java.lang.reflect.ParameterizedType;
// import java.lang.reflect.Type;
import hunt.collection.AbstractMap;
// import hunt.collection.Arrays;
import hunt.collection.Collection;
import hunt.collection.Enumeration;
import hunt.collection.HashMap;
// import hunt.collection.Hashtable;
import hunt.collection.Iterator;
import hunt.collection.Map;
import hunt.collection.Set;
// import hunt.collection.Spliterator;
import hunt.Exceptions;

import hunt.Functions;

// import hunt.collection.concurrent.atomic.AtomicReference;
// import hunt.collection.concurrent.locks.LockSupport;
// import hunt.collection.concurrent.locks.ReentrantLock;
// import java.util.function.BiConsumer;
// import java.util.function.BiFunction;
// import java.util.function.Consumer;
// import java.util.function.DoubleBinaryOperator;
// import java.util.function.Function;
// import java.util.function.IntBinaryOperator;
// import java.util.function.LongBinaryOperator;
// import java.util.function.Predicate;
// import java.util.function.ToDoubleBiFunction;
// import java.util.function.ToDoubleFunction;
// import java.util.function.ToIntBiFunction;
// import java.util.function.ToIntFunction;
// import java.util.function.ToLongBiFunction;
// import java.util.function.ToLongFunction;
// import java.util.stream.Stream;
// import jdk.internal.misc.Unsafe;

// /**
//  * A hash table supporting full concurrency of retrievals and
//  * high expected concurrency for updates. This class obeys the
//  * same functional specification as {@link java.util.Hashtable}, and
//  * includes versions of methods corresponding to each method of
//  * {@code Hashtable}. However, even though all operations are
//  * thread-safe, retrieval operations do <em>not</em> entail locking,
//  * and there is <em>not</em> any support for locking the entire table
//  * in a way that prevents all access.  This class is fully
//  * interoperable with {@code Hashtable} in programs that rely on its
//  * thread safety but not on its synchronization details.
//  *
//  * <p>Retrieval operations (including {@code get}) generally do not
//  * block, so may overlap with update operations (including {@code put}
//  * and {@code remove}). Retrievals reflect the results of the most
//  * recently <em>completed</em> update operations holding upon their
//  * onset. (More formally, an update operation for a given key bears a
//  * <em>happens-before</em> relation with any (non-null) retrieval for
//  * that key reporting the updated value.)  For aggregate operations
//  * such as {@code putAll} and {@code clear}, concurrent retrievals may
//  * reflect insertion or removal of only some entries.  Similarly,
//  * Iterators, Spliterators and Enumerations return elements reflecting the
//  * state of the hash table at some point at or since the creation of the
//  * iterator/enumeration.  They do <em>not</em> throw {@link
//  * java.util.ConcurrentModificationException ConcurrentModificationException}.
//  * However, iterators are designed to be used by only one thread at a time.
//  * Bear in mind that the results of aggregate status methods including
//  * {@code size}, {@code isEmpty}, and {@code containsValue} are typically
//  * useful only when a map is not undergoing concurrent updates in other threads.
//  * Otherwise the results of these methods reflect transient states
//  * that may be adequate for monitoring or estimation purposes, but not
//  * for program control.
//  *
//  * <p>The table is dynamically expanded when there are too many
//  * collisions (i.e., keys that have distinct hash codes but fall into
//  * the same slot modulo the table size), with the expected average
//  * effect of maintaining roughly two bins per mapping (corresponding
//  * to a 0.75 load factor threshold for resizing). There may be much
//  * variance around this average as mappings are added and removed, but
//  * overall, this maintains a commonly accepted time/space tradeoff for
//  * hash tables.  However, resizing this or any other kind of hash
//  * table may be a relatively slow operation. When possible, it is a
//  * good idea to provide a size estimate as an optional {@code
//  * initialCapacity} constructor argument. An additional optional
//  * {@code loadFactor} constructor argument provides a further means of
//  * customizing initial table capacity by specifying the table density
//  * to be used in calculating the amount of space to allocate for the
//  * given number of elements.  Also, for compatibility with previous
//  * versions of this class, constructors may optionally specify an
//  * expected {@code concurrencyLevel} as an additional hint for
//  * internal sizing.  Note that using many keys with exactly the same
//  * {@code hashCode()} is a sure way to slow down performance of any
//  * hash table. To ameliorate impact, when keys are {@link Comparable},
//  * this class may use comparison order among keys to help break ties.
//  *
//  * <p>A {@link Set} projection of a ConcurrentHashMap may be created
//  * (using {@link #newKeySet()} or {@link #newKeySet(int)}), or viewed
//  * (using {@link #keySet(Object)} when only keys are of interest, and the
//  * mapped values are (perhaps transiently) not used or all take the
//  * same mapping value.
//  *
//  * <p>A ConcurrentHashMap can be used as a scalable frequency map (a
//  * form of histogram or multiset) by using {@link
//  * java.util.concurrent.atomic.LongAdder} values and initializing via
//  * {@link #computeIfAbsent computeIfAbsent}. For example, to add a count
//  * to a {@code ConcurrentHashMap<String,LongAdder> freqs}, you can use
//  * {@code freqs.computeIfAbsent(key, k -> new LongAdder()).increment();}
//  *
//  * <p>This class and its views and iterators implement all of the
//  * <em>optional</em> methods of the {@link Map} and {@link Iterator}
//  * interfaces.
//  *
//  * <p>Like {@link Hashtable} but unlike {@link HashMap}, this class
//  * does <em>not</em> allow {@code null} to be used as a key or value.
//  *
//  * <p>ConcurrentHashMaps support a set of sequential and parallel bulk
//  * operations that, unlike most {@link Stream} methods, are designed
//  * to be safely, and often sensibly, applied even with maps that are
//  * being concurrently updated by other threads; for example, when
//  * computing a snapshot summary of the values in a shared registry.
//  * There are three kinds of operation, each with four forms, accepting
//  * functions with keys, values, entries, and (key, value) pairs as
//  * arguments and/or return values. Because the elements of a
//  * ConcurrentHashMap are not ordered in any particular way, and may be
//  * processed in different orders in different parallel executions, the
//  * correctness of supplied functions should not depend on any
//  * ordering, or on any other objects or values that may transiently
//  * change while computation is in progress; and except for forEach
//  * actions, should ideally be side-effect-free. Bulk operations on
//  * {@link Map.Entry} objects do not support method {@code setValue}.
//  *
//  * <ul>
//  * <li>forEach: Performs a given action on each element.
//  * A variant form applies a given transformation on each element
//  * before performing the action.
//  *
//  * <li>search: Returns the first available non-null result of
//  * applying a given function on each element; skipping further
//  * search when a result is found.
//  *
//  * <li>reduce: Accumulates each element.  The supplied reduction
//  * function cannot rely on ordering (more formally, it should be
//  * both associative and commutative).  There are five variants:
//  *
//  * <ul>
//  *
//  * <li>Plain reductions. (There is not a form of this method for
//  * (key, value) function arguments since there is no corresponding
//  * return type.)
//  *
//  * <li>Mapped reductions that accumulate the results of a given
//  * function applied to each element.
//  *
//  * <li>Reductions to scalar doubles, longs, and ints, using a
//  * given basis value.
//  *
//  * </ul>
//  * </ul>
//  *
//  * <p>These bulk operations accept a {@code parallelismThreshold}
//  * argument. Methods proceed sequentially if the current map size is
//  * estimated to be less than the given threshold. Using a value of
//  * {@code Long.MAX_VALUE} suppresses all parallelism.  Using a value
//  * of {@code 1} results in maximal parallelism by partitioning into
//  * enough subtasks to fully utilize the {@link
//  * ForkJoinPool#commonPool()} that is used for all parallel
//  * computations. Normally, you would initially choose one of these
//  * extreme values, and then measure performance of using in-between
//  * values that trade off overhead versus throughput.
//  *
//  * <p>The concurrency properties of bulk operations follow
//  * from those of ConcurrentHashMap: Any non-null result returned
//  * from {@code get(key)} and related access methods bears a
//  * happens-before relation with the associated insertion or
//  * update.  The result of any bulk operation reflects the
//  * composition of these per-element relations (but is not
//  * necessarily atomic with respect to the map as a whole unless it
//  * is somehow known to be quiescent).  Conversely, because keys
//  * and values in the map are never null, null serves as a reliable
//  * atomic indicator of the current lack of any result.  To
//  * maintain this property, null serves as an implicit basis for
//  * all non-scalar reduction operations. For the double, long, and
//  * int versions, the basis should be one that, when combined with
//  * any other value, returns that other value (more formally, it
//  * should be the identity element for the reduction). Most common
//  * reductions have these properties; for example, computing a sum
//  * with basis 0 or a minimum with basis MAX_VALUE.
//  *
//  * <p>Search and transformation functions provided as arguments
//  * should similarly return null to indicate the lack of any result
//  * (in which case it is not used). In the case of mapped
//  * reductions, this also enables transformations to serve as
//  * filters, returning null (or, in the case of primitive
//  * specializations, the identity basis) if the element should not
//  * be combined. You can create compound transformations and
//  * filterings by composing them yourself under this "null means
//  * there is nothing there now" rule before using them in search or
//  * reduce operations.
//  *
//  * <p>Methods accepting and/or returning Entry arguments maintain
//  * key-value associations. They may be useful for example when
//  * finding the key for the greatest value. Note that "plain" Entry
//  * arguments can be supplied using {@code new
//  * AbstractMap.SimpleEntry(k,v)}.
//  *
//  * <p>Bulk operations may complete abruptly, throwing an
//  * exception encountered in the application of a supplied
//  * function. Bear in mind when handling such exceptions that other
//  * concurrently executing functions could also have thrown
//  * exceptions, or would have done so if the first exception had
//  * not occurred.
//  *
//  * <p>Speedups for parallel compared to sequential forms are common
//  * but not guaranteed.  Parallel operations involving brief functions
//  * on small maps may execute more slowly than sequential forms if the
//  * underlying work to parallelize the computation is more expensive
//  * than the computation itself.  Similarly, parallelization may not
//  * lead to much actual parallelism if all processors are busy
//  * performing unrelated tasks.
//  *
//  * <p>All arguments to all task methods must be non-null.
//  *
//  * <p>This class is a member of the
//  * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
//  * Java Collections Framework</a>.
//  *
//  * @author Doug Lea
//  * @param <K> the type of keys maintained by this map
//  * @param <V> the type of mapped values
//  */
// public class ConcurrentHashMap(K, V) : AbstractMap!(K, V), ConcurrentMap!(K, V) { // , Serializable 

//     /*
//      * Overview:
//      *
//      * The primary design goal of this hash table is to maintain
//      * concurrent readability (typically method get(), but also
//      * iterators and related methods) while minimizing update
//      * contention. Secondary goals are to keep space consumption about
//      * the same or better than java.util.HashMap, and to support high
//      * initial insertion rates on an empty table by many threads.
//      *
//      * This map usually acts as a binned (bucketed) hash table.  Each
//      * key-value mapping is held in a Node.  Most nodes are instances
//      * of the basic Node class with hash, key, value, and next
//      * fields. However, various subclasses exist: TreeNodes are
//      * arranged in balanced trees, not lists.  TreeBins hold the roots
//      * of sets of TreeNodes. ForwardingNodes are placed at the heads
//      * of bins during resizing. ReservationNodes are used as
//      * placeholders while establishing values in computeIfAbsent and
//      * related methods.  The types TreeBin, ForwardingNode, and
//      * ReservationNode do not hold normal user keys, values, or
//      * hashes, and are readily distinguishable during search etc
//      * because they have negative hash fields and null key and value
//      * fields. (These special nodes are either uncommon or transient,
//      * so the impact of carrying around some unused fields is
//      * insignificant.)
//      *
//      * The table is lazily initialized to a power-of-two size upon the
//      * first insertion.  Each bin in the table normally contains a
//      * list of Nodes (most often, the list has only zero or one Node).
//      * Table accesses require volatile/atomic reads, writes, and
//      * CASes.  Because there is no other way to arrange this without
//      * adding further indirections, we use intrinsics
//      * (jdk.internal.misc.Unsafe) operations.
//      *
//      * We use the top (sign) bit of Node hash fields for control
//      * purposes -- it is available anyway because of addressing
//      * constraints.  Nodes with negative hash fields are specially
//      * handled or ignored in map methods.
//      *
//      * Insertion (via put or its variants) of the first node in an
//      * empty bin is performed by just CASing it to the bin.  This is
//      * by far the most common case for put operations under most
//      * key/hash distributions.  Other update operations (insert,
//      * delete, and replace) require locks.  We do not want to waste
//      * the space required to associate a distinct lock object with
//      * each bin, so instead use the first node of a bin list itself as
//      * a lock. Locking support for these locks relies on builtin
//      * "synchronized" monitors.
//      *
//      * Using the first node of a list as a lock does not by itself
//      * suffice though: When a node is locked, any update must first
//      * validate that it is still the first node after locking it, and
//      * retry if not. Because new nodes are always appended to lists,
//      * once a node is first in a bin, it remains first until deleted
//      * or the bin becomes invalidated (upon resizing).
//      *
//      * The main disadvantage of per-bin locks is that other update
//      * operations on other nodes in a bin list protected by the same
//      * lock can stall, for example when user equals() or mapping
//      * functions take a long time.  However, statistically, under
//      * random hash codes, this is not a common problem.  Ideally, the
//      * frequency of nodes in bins follows a Poisson distribution
//      * (http://en.wikipedia.org/wiki/Poisson_distribution) with a
//      * parameter of about 0.5 on average, given the resizing threshold
//      * of 0.75, although with a large variance because of resizing
//      * granularity. Ignoring variance, the expected occurrences of
//      * list size k are (exp(-0.5) * pow(0.5, k) / factorial(k)). The
//      * first values are:
//      *
//      * 0:    0.60653066
//      * 1:    0.30326533
//      * 2:    0.07581633
//      * 3:    0.01263606
//      * 4:    0.00157952
//      * 5:    0.00015795
//      * 6:    0.00001316
//      * 7:    0.00000094
//      * 8:    0.00000006
//      * more: less than 1 in ten million
//      *
//      * Lock contention probability for two threads accessing distinct
//      * elements is roughly 1 / (8 * #elements) under random hashes.
//      *
//      * Actual hash code distributions encountered in practice
//      * sometimes deviate significantly from uniform randomness.  This
//      * includes the case when N > (1<<30), so some keys MUST collide.
//      * Similarly for dumb or hostile usages in which multiple keys are
//      * designed to have identical hash codes or ones that differs only
//      * in masked-out high bits. So we use a secondary strategy that
//      * applies when the number of nodes in a bin exceeds a
//      * threshold. These TreeBins use a balanced tree to hold nodes (a
//      * specialized form of red-black trees), bounding search time to
//      * O(log N).  Each search step in a TreeBin is at least twice as
//      * slow as in a regular list, but given that N cannot exceed
//      * (1<<64) (before running out of addresses) this bounds search
//      * steps, lock hold times, etc, to reasonable constants (roughly
//      * 100 nodes inspected per operation worst case) so long as keys
//      * are Comparable (which is very common -- String, Long, etc).
//      * TreeBin nodes (TreeNodes) also maintain the same "next"
//      * traversal pointers as regular nodes, so can be traversed in
//      * iterators in the same way.
//      *
//      * The table is resized when occupancy exceeds a percentage
//      * threshold (nominally, 0.75, but see below).  Any thread
//      * noticing an overfull bin may assist in resizing after the
//      * initiating thread allocates and sets up the replacement array.
//      * However, rather than stalling, these other threads may proceed
//      * with insertions etc.  The use of TreeBins shields us from the
//      * worst case effects of overfilling while resizes are in
//      * progress.  Resizing proceeds by transferring bins, one by one,
//      * from the table to the next table. However, threads claim small
//      * blocks of indices to transfer (via field transferIndex) before
//      * doing so, reducing contention.  A generation stamp in field
//      * sizeCtl ensures that resizings do not overlap. Because we are
//      * using power-of-two expansion, the elements from each bin must
//      * either stay at same index, or move with a power of two
//      * offset. We eliminate unnecessary node creation by catching
//      * cases where old nodes can be reused because their next fields
//      * won't change.  On average, only about one-sixth of them need
//      * cloning when a table doubles. The nodes they replace will be
//      * garbage collectible as soon as they are no longer referenced by
//      * any reader thread that may be in the midst of concurrently
//      * traversing table.  Upon transfer, the old table bin contains
//      * only a special forwarding node (with hash field "MOVED") that
//      * contains the next table as its key. On encountering a
//      * forwarding node, access and update operations restart, using
//      * the new table.
//      *
//      * Each bin transfer requires its bin lock, which can stall
//      * waiting for locks while resizing. However, because other
//      * threads can join in and help resize rather than contend for
//      * locks, average aggregate waits become shorter as resizing
//      * progresses.  The transfer operation must also ensure that all
//      * accessible bins in both the old and new table are usable by any
//      * traversal.  This is arranged in part by proceeding from the
//      * last bin (table.length - 1) up towards the first.  Upon seeing
//      * a forwarding node, traversals (see class Traverser) arrange to
//      * move to the new table without revisiting nodes.  To ensure that
//      * no intervening nodes are skipped even when moved out of order,
//      * a stack (see class TableStack) is created on first encounter of
//      * a forwarding node during a traversal, to maintain its place if
//      * later processing the current table. The need for these
//      * save/restore mechanics is relatively rare, but when one
//      * forwarding node is encountered, typically many more will be.
//      * So Traversers use a simple caching scheme to avoid creating so
//      * many new TableStack nodes. (Thanks to Peter Levart for
//      * suggesting use of a stack here.)
//      *
//      * The traversal scheme also applies to partial traversals of
//      * ranges of bins (via an alternate Traverser constructor)
//      * to support partitioned aggregate operations.  Also, read-only
//      * operations give up if ever forwarded to a null table, which
//      * provides support for shutdown-style clearing, which is also not
//      * currently implemented.
//      *
//      * Lazy table initialization minimizes footprint until first use,
//      * and also avoids resizings when the first operation is from a
//      * putAll, constructor with map argument, or deserialization.
//      * These cases attempt to override the initial capacity settings,
//      * but harmlessly fail to take effect in cases of races.
//      *
//      * The element count is maintained using a specialization of
//      * LongAdder. We need to incorporate a specialization rather than
//      * just use a LongAdder in order to access implicit
//      * contention-sensing that leads to creation of multiple
//      * CounterCells.  The counter mechanics avoid contention on
//      * updates but can encounter cache thrashing if read too
//      * frequently during concurrent access. To avoid reading so often,
//      * resizing under contention is attempted only upon adding to a
//      * bin already holding two or more nodes. Under uniform hash
//      * distributions, the probability of this occurring at threshold
//      * is around 13%, meaning that only about 1 in 8 puts check
//      * threshold (and after resizing, many fewer do so).
//      *
//      * TreeBins use a special form of comparison for search and
//      * related operations (which is the main reason we cannot use
//      * existing collections such as TreeMaps). TreeBins contain
//      * Comparable elements, but may contain others, as well as
//      * elements that are Comparable but not necessarily Comparable for
//      * the same T, so we cannot invoke compareTo among them. To handle
//      * this, the tree is ordered primarily by hash value, then by
//      * Comparable.compareTo order if applicable.  On lookup at a node,
//      * if elements are not comparable or compare as 0 then both left
//      * and right children may need to be searched in the case of tied
//      * hash values. (This corresponds to the full list search that
//      * would be necessary if all elements were non-Comparable and had
//      * tied hashes.) On insertion, to keep a total ordering (or as
//      * close as is required here) across rebalancings, we compare
//      * classes and identityHashCodes as tie-breakers. The red-black
//      * balancing code is updated from pre-jdk-collections
//      * (http://gee.cs.oswego.edu/dl/classes/collections/RBCell.java)
//      * based in turn on Cormen, Leiserson, and Rivest "Introduction to
//      * Algorithms" (CLR).
//      *
//      * TreeBins also require an additional locking mechanism.  While
//      * list traversal is always possible by readers even during
//      * updates, tree traversal is not, mainly because of tree-rotations
//      * that may change the root node and/or its linkages.  TreeBins
//      * include a simple read-write lock mechanism parasitic on the
//      * main bin-synchronization strategy: Structural adjustments
//      * associated with an insertion or removal are already bin-locked
//      * (and so cannot conflict with other writers) but must wait for
//      * ongoing readers to finish. Since there can be only one such
//      * waiter, we use a simple scheme using a single "waiter" field to
//      * block writers.  However, readers need never block.  If the root
//      * lock is held, they proceed along the slow traversal path (via
//      * next-pointers) until the lock becomes available or the list is
//      * exhausted, whichever comes first. These cases are not fast, but
//      * maximize aggregate expected throughput.
//      *
//      * Maintaining API and serialization compatibility with previous
//      * versions of this class introduces several oddities. Mainly: We
//      * leave untouched but unused constructor arguments referring to
//      * concurrencyLevel. We accept a loadFactor constructor argument,
//      * but apply it only to initial table capacity (which is the only
//      * time that we can guarantee to honor it.) We also declare an
//      * unused "Segment" class that is instantiated in minimal form
//      * only when serializing.
//      *
//      * Also, solely for compatibility with previous versions of this
//      * class, it extends AbstractMap, even though all of its methods
//      * are overridden, so it is just useless baggage.
//      *
//      * This file is organized to make things a little easier to follow
//      * while reading than they might otherwise: First the main static
//      * declarations and utilities, then fields, then main public
//      * methods (with a few factorings of multiple public methods into
//      * internal ones), then sizing methods, trees, traversers, and
//      * bulk operations.
//      */

//     /* ---------------- Constants -------------- */

//     /**
//      * The largest possible table capacity.  This value must be
//      * exactly 1<<30 to stay within Java array allocation and indexing
//      * bounds for power of two table sizes, and is further required
//      * because the top two bits of 32bit hash fields are used for
//      * control purposes.
//      */
//     private enum int MAXIMUM_CAPACITY = 1 << 30;

//     /**
//      * The default initial table capacity.  Must be a power of 2
//      * (i.e., at least 1) and at most MAXIMUM_CAPACITY.
//      */
//     private enum int DEFAULT_CAPACITY = 16;

//     /**
//      * The largest possible (non-power of two) array size.
//      * Needed by toArray and related methods.
//      */
//     enum int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;

//     /**
//      * The default concurrency level for this table. Unused but
//      * defined for compatibility with previous versions of this class.
//      */
//     private enum int DEFAULT_CONCURRENCY_LEVEL = 16;

//     /**
//      * The load factor for this table. Overrides of this value in
//      * constructors affect only the initial table capacity.  The
//      * actual floating point value isn't normally used -- it is
//      * simpler to use expressions such as {@code n - (n >>> 2)} for
//      * the associated resizing threshold.
//      */
//     private enum float LOAD_FACTOR = 0.75f;

//     /**
//      * The bin count threshold for using a tree rather than list for a
//      * bin.  Bins are converted to trees when adding an element to a
//      * bin with at least this many nodes. The value must be greater
//      * than 2, and should be at least 8 to mesh with assumptions in
//      * tree removal about conversion back to plain bins upon
//      * shrinkage.
//      */
//     enum int TREEIFY_THRESHOLD = 8;

//     /**
//      * The bin count threshold for untreeifying a (split) bin during a
//      * resize operation. Should be less than TREEIFY_THRESHOLD, and at
//      * most 6 to mesh with shrinkage detection under removal.
//      */
//     enum int UNTREEIFY_THRESHOLD = 6;

//     /**
//      * The smallest table capacity for which bins may be treeified.
//      * (Otherwise the table is resized if too many nodes in a bin.)
//      * The value should be at least 4 * TREEIFY_THRESHOLD to avoid
//      * conflicts between resizing and treeification thresholds.
//      */
//     enum int MIN_TREEIFY_CAPACITY = 64;

//     /**
//      * Minimum number of rebinnings per transfer step. Ranges are
//      * subdivided to allow multiple resizer threads.  This value
//      * serves as a lower bound to avoid resizers encountering
//      * excessive memory contention.  The value should be at least
//      * DEFAULT_CAPACITY.
//      */
//     private enum int MIN_TRANSFER_STRIDE = 16;

//     /**
//      * The number of bits used for generation stamp in sizeCtl.
//      * Must be at least 6 for 32bit arrays.
//      */
//     private enum int RESIZE_STAMP_BITS = 16;

//     /**
//      * The maximum number of threads that can help resize.
//      * Must fit in 32 - RESIZE_STAMP_BITS bits.
//      */
//     private enum int MAX_RESIZERS = (1 << (32 - RESIZE_STAMP_BITS)) - 1;

//     /**
//      * The bit shift for recording size stamp in sizeCtl.
//      */
//     private enum int RESIZE_STAMP_SHIFT = 32 - RESIZE_STAMP_BITS;

//     /*
//      * Encodings for Node hash fields. See above for explanation.
//      */
//     enum int MOVED     = -1; // hash for forwarding nodes
//     enum int TREEBIN   = -2; // hash for roots of trees
//     enum int RESERVED  = -3; // hash for transient reservations
//     enum int HASH_BITS = 0x7fffffff; // usable bits of normal node hash

//     /** Number of CPUS, to place bounds on some sizings */
//     enum int NCPU = Runtime.getRuntime().availableProcessors();

//     /**
//      * Serialized pseudo-fields, provided only for jdk7 compatibility.
//      * @serialField segments Segment[]
//      *   The segments, each of which is a specialized hash table.
//      * @serialField segmentMask int
//      *   Mask value for indexing into segments. The upper bits of a
//      *   key's hash code are used to choose the segment.
//      * @serialField segmentShift int
//      *   Shift value for indexing within segments.
//      */
//     private static final ObjectStreamField[] serialPersistentFields = {
//         new ObjectStreamField("segments", Segment[].class),
//         new ObjectStreamField("segmentMask", Integer.TYPE),
//         new ObjectStreamField("segmentShift", Integer.TYPE),
//     };

//     /* ---------------- Nodes -------------- */

//     /**
//      * Key-value entry.  This class is never exported out as a
//      * user-mutable Map.Entry (i.e., one supporting setValue; see
//      * MapEntry below), but can be used for read-only traversals used
//      * in bulk tasks.  Subclasses of Node with a negative hash field
//      * are special, and contain null keys and values (but are never
//      * exported).  Otherwise, keys and vals are never null.
//      */
//     static class Node!(K, V) implements Map.Entry!(K, V) {
//         final int hash;
//         final K key;
//         volatile V val;
//         volatile Node!(K, V) next;

//         Node(int hash, K key, V val) {
//             this.hash = hash;
//             this.key = key;
//             this.val = val;
//         }

//         Node(int hash, K key, V val, Node!(K, V) next) {
//             this(hash, key, val);
//             this.next = next;
//         }

//         public final K getKey()     { return key; }
//         public final V getValue()   { return val; }
//         public final int hashCode() { return key.hashCode() ^ val.hashCode(); }
//         public final String toString() {
//             return Helpers.mapEntryToString(key, val);
//         }
//         public final V setValue(V value) {
//             throw new UnsupportedOperationException();
//         }

//         public final boolean equals(Object o) {
//             Object k, v, u; Map.Entry<?,?> e;
//             return ((o instanceof Map.Entry) &&
//                     (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
//                     (v = e.getValue()) != null &&
//                     (k == key || k.equals(key)) &&
//                     (v == (u = val) || v.equals(u)));
//         }

//         /**
//          * Virtualized support for map.get(); overridden in subclasses.
//          */
//         Node!(K, V) find(int h, Object k) {
//             Node!(K, V) e = this;
//             if (k != null) {
//                 do {
//                     K ek;
//                     if (e.hash == h &&
//                         ((ek = e.key) == k || (ek != null && k.equals(ek))))
//                         return e;
//                 } while ((e = e.next) != null);
//             }
//             return null;
//         }
//     }

//     /* ---------------- Static utilities -------------- */

//     /**
//      * Spreads (XORs) higher bits of hash to lower and also forces top
//      * bit to 0. Because the table uses power-of-two masking, sets of
//      * hashes that vary only in bits above the current mask will
//      * always collide. (Among known examples are sets of Float keys
//      * holding consecutive whole numbers in small tables.)  So we
//      * apply a transform that spreads the impact of higher bits
//      * downward. There is a tradeoff between speed, utility, and
//      * quality of bit-spreading. Because many common sets of hashes
//      * are already reasonably distributed (so don't benefit from
//      * spreading), and because we use trees to handle large sets of
//      * collisions in bins, we just XOR some shifted bits in the
//      * cheapest possible way to reduce systematic lossage, as well as
//      * to incorporate impact of the highest bits that would otherwise
//      * never be used in index calculations because of table bounds.
//      */
//     static final int spread(int h) {
//         return (h ^ (h >>> 16)) & HASH_BITS;
//     }

//     /**
//      * Returns a power of two table size for the given desired capacity.
//      * See Hackers Delight, sec 3.2
//      */
//     private static final int tableSizeFor(int c) {
//         int n = -1 >>> Integer.numberOfLeadingZeros(c - 1);
//         return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;
//     }

//     /**
//      * Returns x's Class if it is of the form "class C implements
//      * Comparable<C>", else null.
//      */
//     static Class<?> comparableClassFor(Object x) {
//         if (x instanceof Comparable) {
//             Class<?> c; Type[] ts, as; ParameterizedType p;
//             if ((c = x.getClass()) == String.class) // bypass checks
//                 return c;
//             if ((ts = c.getGenericInterfaces()) != null) {
//                 for (Type t : ts) {
//                     if ((t instanceof ParameterizedType) &&
//                         ((p = (ParameterizedType)t).getRawType() ==
//                          Comparable.class) &&
//                         (as = p.getActualTypeArguments()) != null &&
//                         as.length == 1 && as[0] == c) // type arg is c
//                         return c;
//                 }
//             }
//         }
//         return null;
//     }

//     /**
//      * Returns k.compareTo(x) if x matches kc (k's screened comparable
//      * class), else 0.
//      */
//     @SuppressWarnings({"rawtypes","unchecked"}) // for cast to Comparable
//     static int compareComparables(Class<?> kc, Object k, Object x) {
//         return (x == null || x.getClass() != kc ? 0 :
//                 ((Comparable)k).compareTo(x));
//     }

//     /* ---------------- Table element access -------------- */

//     /*
//      * Atomic access methods are used for table elements as well as
//      * elements of in-progress next table while resizing.  All uses of
//      * the tab arguments must be null checked by callers.  All callers
//      * also paranoically precheck that tab's length is not zero (or an
//      * equivalent check), thus ensuring that any index argument taking
//      * the form of a hash value anded with (length - 1) is a valid
//      * index.  Note that, to be correct wrt arbitrary concurrency
//      * errors by users, these checks must operate on local variables,
//      * which accounts for some odd-looking inline assignments below.
//      * Note that calls to setTabAt always occur within locked regions,
//      * and so require only release ordering.
//      */

    
//     static final !(K, V) Node!(K, V) tabAt(Node!(K, V)[] tab, int i) {
//         return (Node!(K, V))U.getObjectAcquire(tab, ((long)i << ASHIFT) + ABASE);
//     }

//     static final !(K, V) boolean casTabAt(Node!(K, V)[] tab, int i,
//                                         Node!(K, V) c, Node!(K, V) v) {
//         return U.compareAndSetObject(tab, ((long)i << ASHIFT) + ABASE, c, v);
//     }

//     static final !(K, V) void setTabAt(Node!(K, V)[] tab, int i, Node!(K, V) v) {
//         U.putObjectRelease(tab, ((long)i << ASHIFT) + ABASE, v);
//     }

//     /* ---------------- Fields -------------- */

//     /**
//      * The array of bins. Lazily initialized upon first insertion.
//      * Size is always a power of two. Accessed directly by iterators.
//      */
//     transient volatile Node!(K, V)[] table;

//     /**
//      * The next table to use; non-null only while resizing.
//      */
//     private transient volatile Node!(K, V)[] nextTable;

//     /**
//      * Base counter value, used mainly when there is no contention,
//      * but also as a fallback during table initialization
//      * races. Updated via CAS.
//      */
//     private transient volatile long baseCount;

//     /**
//      * Table initialization and resizing control.  When negative, the
//      * table is being initialized or resized: -1 for initialization,
//      * else -(1 + the number of active resizing threads).  Otherwise,
//      * when table is null, holds the initial table size to use upon
//      * creation, or 0 for default. After initialization, holds the
//      * next element count value upon which to resize the table.
//      */
//     private transient volatile int sizeCtl;

//     /**
//      * The next table index (plus one) to split while resizing.
//      */
//     private transient volatile int transferIndex;

//     /**
//      * Spinlock (locked via CAS) used when resizing and/or creating CounterCells.
//      */
//     private transient volatile int cellsBusy;

//     /**
//      * Table of counter cells. When non-null, size is a power of 2.
//      */
//     private transient volatile CounterCell[] counterCells;

//     // views
//     private transient KeySetView!(K, V) keySet;
//     private transient ValuesView!(K, V) values;
//     private transient EntrySetView!(K, V) entrySet;


//     /* ---------------- Public operations -------------- */

//     /**
//      * Creates a new, empty map with the default initial table size (16).
//      */
//     public ConcurrentHashMap() {
//     }

//     /**
//      * Creates a new, empty map with an initial table size
//      * accommodating the specified number of elements without the need
//      * to dynamically resize.
//      *
//      * @param initialCapacity The implementation performs internal
//      * sizing to accommodate this many elements.
//      * @throws IllegalArgumentException if the initial capacity of
//      * elements is negative
//      */
//     public ConcurrentHashMap(int initialCapacity) {
//         this(initialCapacity, LOAD_FACTOR, 1);
//     }

//     /**
//      * Creates a new map with the same mappings as the given map.
//      *
//      * @param m the map
//      */
//     public ConcurrentHashMap(Map<? extends K, ? extends V> m) {
//         this.sizeCtl = DEFAULT_CAPACITY;
//         putAll(m);
//     }

//     /**
//      * Creates a new, empty map with an initial table size based on
//      * the given number of elements ({@code initialCapacity}) and
//      * initial table density ({@code loadFactor}).
//      *
//      * @param initialCapacity the initial capacity. The implementation
//      * performs internal sizing to accommodate this many elements,
//      * given the specified load factor.
//      * @param loadFactor the load factor (table density) for
//      * establishing the initial table size
//      * @throws IllegalArgumentException if the initial capacity of
//      * elements is negative or the load factor is nonpositive
//      *
//      */
//     public ConcurrentHashMap(int initialCapacity, float loadFactor) {
//         this(initialCapacity, loadFactor, 1);
//     }

//     /**
//      * Creates a new, empty map with an initial table size based on
//      * the given number of elements ({@code initialCapacity}), initial
//      * table density ({@code loadFactor}), and number of concurrently
//      * updating threads ({@code concurrencyLevel}).
//      *
//      * @param initialCapacity the initial capacity. The implementation
//      * performs internal sizing to accommodate this many elements,
//      * given the specified load factor.
//      * @param loadFactor the load factor (table density) for
//      * establishing the initial table size
//      * @param concurrencyLevel the estimated number of concurrently
//      * updating threads. The implementation may use this value as
//      * a sizing hint.
//      * @throws IllegalArgumentException if the initial capacity is
//      * negative or the load factor or concurrencyLevel are
//      * nonpositive
//      */
//     public ConcurrentHashMap(int initialCapacity,
//                              float loadFactor, int concurrencyLevel) {
//         if (!(loadFactor > 0.0f) || initialCapacity < 0 || concurrencyLevel <= 0)
//             throw new IllegalArgumentException();
//         if (initialCapacity < concurrencyLevel)   // Use at least as many bins
//             initialCapacity = concurrencyLevel;   // as estimated threads
//         long size = (long)(1.0 + (long)initialCapacity / loadFactor);
//         int cap = (size >= (long)MAXIMUM_CAPACITY) ?
//             MAXIMUM_CAPACITY : tableSizeFor((int)size);
//         this.sizeCtl = cap;
//     }

//     // Original (since JDK1.2) Map methods

//     /**
//      * {@inheritDoc}
//      */
//     public int size() {
//         long n = sumCount();
//         return ((n < 0L) ? 0 :
//                 (n > (long)Integer.MAX_VALUE) ? Integer.MAX_VALUE :
//                 (int)n);
//     }

//     /**
//      * {@inheritDoc}
//      */
//     public boolean isEmpty() {
//         return sumCount() <= 0L; // ignore transient negative values
//     }

//     /**
//      * Returns the value to which the specified key is mapped,
//      * or {@code null} if this map contains no mapping for the key.
//      *
//      * <p>More formally, if this map contains a mapping from a key
//      * {@code k} to a value {@code v} such that {@code key.equals(k)},
//      * then this method returns {@code v}; otherwise it returns
//      * {@code null}.  (There can be at most one such mapping.)
//      *
//      * @throws NullPointerException if the specified key is null
//      */
//     public V get(Object key) {
//         Node!(K, V)[] tab; Node!(K, V) e, p; int n, eh; K ek;
//         int h = spread(key.hashCode());
//         if ((tab = table) != null && (n = tab.length) > 0 &&
//             (e = tabAt(tab, (n - 1) & h)) != null) {
//             if ((eh = e.hash) == h) {
//                 if ((ek = e.key) == key || (ek != null && key.equals(ek)))
//                     return e.val;
//             }
//             else if (eh < 0)
//                 return (p = e.find(h, key)) != null ? p.val : null;
//             while ((e = e.next) != null) {
//                 if (e.hash == h &&
//                     ((ek = e.key) == key || (ek != null && key.equals(ek))))
//                     return e.val;
//             }
//         }
//         return null;
//     }

//     /**
//      * Tests if the specified object is a key in this table.
//      *
//      * @param  key possible key
//      * @return {@code true} if and only if the specified object
//      *         is a key in this table, as determined by the
//      *         {@code equals} method; {@code false} otherwise
//      * @throws NullPointerException if the specified key is null
//      */
//     public boolean containsKey(Object key) {
//         return get(key) != null;
//     }

//     /**
//      * Returns {@code true} if this map maps one or more keys to the
//      * specified value. Note: This method may require a full traversal
//      * of the map, and is much slower than method {@code containsKey}.
//      *
//      * @param value value whose presence in this map is to be tested
//      * @return {@code true} if this map maps one or more keys to the
//      *         specified value
//      * @throws NullPointerException if the specified value is null
//      */
//     public boolean containsValue(Object value) {
//         if (value == null)
//             throw new NullPointerException();
//         Node!(K, V)[] t;
//         if ((t = table) != null) {
//             Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//             for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                 V v;
//                 if ((v = p.val) == value || (v != null && value.equals(v)))
//                     return true;
//             }
//         }
//         return false;
//     }

//     /**
//      * Maps the specified key to the specified value in this table.
//      * Neither the key nor the value can be null.
//      *
//      * <p>The value can be retrieved by calling the {@code get} method
//      * with a key that is equal to the original key.
//      *
//      * @param key key with which the specified value is to be associated
//      * @param value value to be associated with the specified key
//      * @return the previous value associated with {@code key}, or
//      *         {@code null} if there was no mapping for {@code key}
//      * @throws NullPointerException if the specified key or value is null
//      */
//     public V put(K key, V value) {
//         return putVal(key, value, false);
//     }

//     /** Implementation for put and putIfAbsent */
//     final V putVal(K key, V value, boolean onlyIfAbsent) {
//         if (key == null || value == null) throw new NullPointerException();
//         int hash = spread(key.hashCode());
//         int binCount = 0;
//         for (Node!(K, V)[] tab = table;;) {
//             Node!(K, V) f; int n, i, fh; K fk; V fv;
//             if (tab == null || (n = tab.length) == 0)
//                 tab = initTable();
//             else if ((f = tabAt(tab, i = (n - 1) & hash)) == null) {
//                 if (casTabAt(tab, i, null, new Node!(K, V)(hash, key, value)))
//                     break;                   // no lock when adding to empty bin
//             }
//             else if ((fh = f.hash) == MOVED)
//                 tab = helpTransfer(tab, f);
//             else if (onlyIfAbsent // check first node without acquiring lock
//                      && fh == hash
//                      && ((fk = f.key) == key || (fk != null && key.equals(fk)))
//                      && (fv = f.val) != null)
//                 return fv;
//             else {
//                 V oldVal = null;
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         if (fh >= 0) {
//                             binCount = 1;
//                             for (Node!(K, V) e = f;; ++binCount) {
//                                 K ek;
//                                 if (e.hash == hash &&
//                                     ((ek = e.key) == key ||
//                                      (ek != null && key.equals(ek)))) {
//                                     oldVal = e.val;
//                                     if (!onlyIfAbsent)
//                                         e.val = value;
//                                     break;
//                                 }
//                                 Node!(K, V) pred = e;
//                                 if ((e = e.next) == null) {
//                                     pred.next = new Node!(K, V)(hash, key, value);
//                                     break;
//                                 }
//                             }
//                         }
//                         else if (f instanceof TreeBin) {
//                             Node!(K, V) p;
//                             binCount = 2;
//                             if ((p = ((TreeBin!(K, V))f).putTreeVal(hash, key,
//                                                            value)) != null) {
//                                 oldVal = p.val;
//                                 if (!onlyIfAbsent)
//                                     p.val = value;
//                             }
//                         }
//                         else if (f instanceof ReservationNode)
//                             throw new IllegalStateException("Recursive update");
//                     }
//                 }
//                 if (binCount != 0) {
//                     if (binCount >= TREEIFY_THRESHOLD)
//                         treeifyBin(tab, i);
//                     if (oldVal != null)
//                         return oldVal;
//                     break;
//                 }
//             }
//         }
//         addCount(1L, binCount);
//         return null;
//     }

//     /**
//      * Copies all of the mappings from the specified map to this one.
//      * These mappings replace any mappings that this map had for any of the
//      * keys currently in the specified map.
//      *
//      * @param m mappings to be stored in this map
//      */
//     public void putAll(Map<? extends K, ? extends V> m) {
//         tryPresize(m.size());
//         for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
//             putVal(e.getKey(), e.getValue(), false);
//     }

//     /**
//      * Removes the key (and its corresponding value) from this map.
//      * This method does nothing if the key is not in the map.
//      *
//      * @param  key the key that needs to be removed
//      * @return the previous value associated with {@code key}, or
//      *         {@code null} if there was no mapping for {@code key}
//      * @throws NullPointerException if the specified key is null
//      */
//     public V remove(Object key) {
//         return replaceNode(key, null, null);
//     }

//     /**
//      * Implementation for the four public remove/replace methods:
//      * Replaces node value with v, conditional upon match of cv if
//      * non-null.  If resulting value is null, delete.
//      */
//     final V replaceNode(Object key, V value, Object cv) {
//         int hash = spread(key.hashCode());
//         for (Node!(K, V)[] tab = table;;) {
//             Node!(K, V) f; int n, i, fh;
//             if (tab == null || (n = tab.length) == 0 ||
//                 (f = tabAt(tab, i = (n - 1) & hash)) == null)
//                 break;
//             else if ((fh = f.hash) == MOVED)
//                 tab = helpTransfer(tab, f);
//             else {
//                 V oldVal = null;
//                 boolean validated = false;
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         if (fh >= 0) {
//                             validated = true;
//                             for (Node!(K, V) e = f, pred = null;;) {
//                                 K ek;
//                                 if (e.hash == hash &&
//                                     ((ek = e.key) == key ||
//                                      (ek != null && key.equals(ek)))) {
//                                     V ev = e.val;
//                                     if (cv == null || cv == ev ||
//                                         (ev != null && cv.equals(ev))) {
//                                         oldVal = ev;
//                                         if (value != null)
//                                             e.val = value;
//                                         else if (pred != null)
//                                             pred.next = e.next;
//                                         else
//                                             setTabAt(tab, i, e.next);
//                                     }
//                                     break;
//                                 }
//                                 pred = e;
//                                 if ((e = e.next) == null)
//                                     break;
//                             }
//                         }
//                         else if (f instanceof TreeBin) {
//                             validated = true;
//                             TreeBin!(K, V) t = (TreeBin!(K, V))f;
//                             TreeNode!(K, V) r, p;
//                             if ((r = t.root) != null &&
//                                 (p = r.findTreeNode(hash, key, null)) != null) {
//                                 V pv = p.val;
//                                 if (cv == null || cv == pv ||
//                                     (pv != null && cv.equals(pv))) {
//                                     oldVal = pv;
//                                     if (value != null)
//                                         p.val = value;
//                                     else if (t.removeTreeNode(p))
//                                         setTabAt(tab, i, untreeify(t.first));
//                                 }
//                             }
//                         }
//                         else if (f instanceof ReservationNode)
//                             throw new IllegalStateException("Recursive update");
//                     }
//                 }
//                 if (validated) {
//                     if (oldVal != null) {
//                         if (value == null)
//                             addCount(-1L, -1);
//                         return oldVal;
//                     }
//                     break;
//                 }
//             }
//         }
//         return null;
//     }

//     /**
//      * Removes all of the mappings from this map.
//      */
//     public void clear() {
//         long delta = 0L; // negative number of deletions
//         int i = 0;
//         Node!(K, V)[] tab = table;
//         while (tab != null && i < tab.length) {
//             int fh;
//             Node!(K, V) f = tabAt(tab, i);
//             if (f == null)
//                 ++i;
//             else if ((fh = f.hash) == MOVED) {
//                 tab = helpTransfer(tab, f);
//                 i = 0; // restart
//             }
//             else {
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         Node!(K, V) p = (fh >= 0 ? f :
//                                        (f instanceof TreeBin) ?
//                                        ((TreeBin!(K, V))f).first : null);
//                         while (p != null) {
//                             --delta;
//                             p = p.next;
//                         }
//                         setTabAt(tab, i++, null);
//                     }
//                 }
//             }
//         }
//         if (delta != 0L)
//             addCount(delta, -1);
//     }

//     /**
//      * Returns a {@link Set} view of the keys contained in this map.
//      * The set is backed by the map, so changes to the map are
//      * reflected in the set, and vice-versa. The set supports element
//      * removal, which removes the corresponding mapping from this map,
//      * via the {@code Iterator.remove}, {@code Set.remove},
//      * {@code removeAll}, {@code retainAll}, and {@code clear}
//      * operations.  It does not support the {@code add} or
//      * {@code addAll} operations.
//      *
//      * <p>The view's iterators and spliterators are
//      * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
//      *
//      * <p>The view's {@code spliterator} reports {@link Spliterator#CONCURRENT},
//      * {@link Spliterator#DISTINCT}, and {@link Spliterator#NONNULL}.
//      *
//      * @return the set view
//      */
//     public KeySetView!(K, V) keySet() {
//         KeySetView!(K, V) ks;
//         if ((ks = keySet) != null) return ks;
//         return keySet = new KeySetView!(K, V)(this, null);
//     }

//     /**
//      * Returns a {@link Collection} view of the values contained in this map.
//      * The collection is backed by the map, so changes to the map are
//      * reflected in the collection, and vice-versa.  The collection
//      * supports element removal, which removes the corresponding
//      * mapping from this map, via the {@code Iterator.remove},
//      * {@code Collection.remove}, {@code removeAll},
//      * {@code retainAll}, and {@code clear} operations.  It does not
//      * support the {@code add} or {@code addAll} operations.
//      *
//      * <p>The view's iterators and spliterators are
//      * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
//      *
//      * <p>The view's {@code spliterator} reports {@link Spliterator#CONCURRENT}
//      * and {@link Spliterator#NONNULL}.
//      *
//      * @return the collection view
//      */
//     public Collection<V> values() {
//         ValuesView!(K, V) vs;
//         if ((vs = values) != null) return vs;
//         return values = new ValuesView!(K, V)(this);
//     }

//     /**
//      * Returns a {@link Set} view of the mappings contained in this map.
//      * The set is backed by the map, so changes to the map are
//      * reflected in the set, and vice-versa.  The set supports element
//      * removal, which removes the corresponding mapping from the map,
//      * via the {@code Iterator.remove}, {@code Set.remove},
//      * {@code removeAll}, {@code retainAll}, and {@code clear}
//      * operations.
//      *
//      * <p>The view's iterators and spliterators are
//      * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
//      *
//      * <p>The view's {@code spliterator} reports {@link Spliterator#CONCURRENT},
//      * {@link Spliterator#DISTINCT}, and {@link Spliterator#NONNULL}.
//      *
//      * @return the set view
//      */
//     public Set<Map.Entry!(K, V)> entrySet() {
//         EntrySetView!(K, V) es;
//         if ((es = entrySet) != null) return es;
//         return entrySet = new EntrySetView!(K, V)(this);
//     }

//     /**
//      * Returns the hash code value for this {@link Map}, i.e.,
//      * the sum of, for each key-value pair in the map,
//      * {@code key.hashCode() ^ value.hashCode()}.
//      *
//      * @return the hash code value for this map
//      */
//     public int hashCode() {
//         int h = 0;
//         Node!(K, V)[] t;
//         if ((t = table) != null) {
//             Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//             for (Node!(K, V) p; (p = it.advance()) != null; )
//                 h += p.key.hashCode() ^ p.val.hashCode();
//         }
//         return h;
//     }

//     /**
//      * Returns a string representation of this map.  The string
//      * representation consists of a list of key-value mappings (in no
//      * particular order) enclosed in braces ("{@code {}}").  Adjacent
//      * mappings are separated by the characters {@code ", "} (comma
//      * and space).  Each key-value mapping is rendered as the key
//      * followed by an equals sign ("{@code =}") followed by the
//      * associated value.
//      *
//      * @return a string representation of this map
//      */
//     public String toString() {
//         Node!(K, V)[] t;
//         int f = (t = table) == null ? 0 : t.length;
//         Traverser!(K, V) it = new Traverser!(K, V)(t, f, 0, f);
//         StringBuilder sb = new StringBuilder();
//         sb.append('{');
//         Node!(K, V) p;
//         if ((p = it.advance()) != null) {
//             for (;;) {
//                 K k = p.key;
//                 V v = p.val;
//                 sb.append(k == this ? "(this Map)" : k);
//                 sb.append('=');
//                 sb.append(v == this ? "(this Map)" : v);
//                 if ((p = it.advance()) == null)
//                     break;
//                 sb.append(',').append(' ');
//             }
//         }
//         return sb.append('}').toString();
//     }

//     /**
//      * Compares the specified object with this map for equality.
//      * Returns {@code true} if the given object is a map with the same
//      * mappings as this map.  This operation may return misleading
//      * results if either map is concurrently modified during execution
//      * of this method.
//      *
//      * @param o object to be compared for equality with this map
//      * @return {@code true} if the specified object is equal to this map
//      */
//     public boolean equals(Object o) {
//         if (o != this) {
//             if (!(o instanceof Map))
//                 return false;
//             Map<?,?> m = (Map<?,?>) o;
//             Node!(K, V)[] t;
//             int f = (t = table) == null ? 0 : t.length;
//             Traverser!(K, V) it = new Traverser!(K, V)(t, f, 0, f);
//             for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                 V val = p.val;
//                 Object v = m.get(p.key);
//                 if (v == null || (v != val && !v.equals(val)))
//                     return false;
//             }
//             for (Map.Entry<?,?> e : m.entrySet()) {
//                 Object mk, mv, v;
//                 if ((mk = e.getKey()) == null ||
//                     (mv = e.getValue()) == null ||
//                     (v = get(mk)) == null ||
//                     (mv != v && !mv.equals(v)))
//                     return false;
//             }
//         }
//         return true;
//     }

//     /**
//      * Stripped-down version of helper class used in previous version,
//      * declared for the sake of serialization compatibility.
//      */
//     static class Segment!(K, V) extends ReentrantLock implements Serializable {
//         private static final long serialVersionUID = 2249069246763182397L;
//         final float loadFactor;
//         Segment(float lf) { this.loadFactor = lf; }
//     }

//     /**
//      * Saves this map to a stream (that is, serializes it).
//      *
//      * @param s the stream
//      * @throws java.io.IOException if an I/O error occurs
//      * @serialData
//      * the serialized fields, followed by the key (Object) and value
//      * (Object) for each key-value mapping, followed by a null pair.
//      * The key-value mappings are emitted in no particular order.
//      */
//     private void writeObject(java.io.ObjectOutputStream s)
//         throws java.io.IOException {
//         // For serialization compatibility
//         // Emulate segment calculation from previous version of this class
//         int sshift = 0;
//         int ssize = 1;
//         while (ssize < DEFAULT_CONCURRENCY_LEVEL) {
//             ++sshift;
//             ssize <<= 1;
//         }
//         int segmentShift = 32 - sshift;
//         int segmentMask = ssize - 1;
        
//         Segment!(K, V)[] segments = (Segment!(K, V)[])
//             new Segment<?,?>[DEFAULT_CONCURRENCY_LEVEL];
//         for (int i = 0; i < segments.length; ++i)
//             segments[i] = new Segment!(K, V)(LOAD_FACTOR);
//         java.io.ObjectOutputStream.PutField streamFields = s.putFields();
//         streamFields.put("segments", segments);
//         streamFields.put("segmentShift", segmentShift);
//         streamFields.put("segmentMask", segmentMask);
//         s.writeFields();

//         Node!(K, V)[] t;
//         if ((t = table) != null) {
//             Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//             for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                 s.writeObject(p.key);
//                 s.writeObject(p.val);
//             }
//         }
//         s.writeObject(null);
//         s.writeObject(null);
//     }

//     /**
//      * Reconstitutes this map from a stream (that is, deserializes it).
//      * @param s the stream
//      * @throws ClassNotFoundException if the class of a serialized object
//      *         could not be found
//      * @throws java.io.IOException if an I/O error occurs
//      */
//     private void readObject(java.io.ObjectInputStream s)
//         throws java.io.IOException, ClassNotFoundException {
//         /*
//          * To improve performance in typical cases, we create nodes
//          * while reading, then place in table once size is known.
//          * However, we must also validate uniqueness and deal with
//          * overpopulated bins while doing so, which requires
//          * specialized versions of putVal mechanics.
//          */
//         sizeCtl = -1; // force exclusion for table construction
//         s.defaultReadObject();
//         long size = 0L;
//         Node!(K, V) p = null;
//         for (;;) {
            
//             K k = (K) s.readObject();
            
//             V v = (V) s.readObject();
//             if (k != null && v != null) {
//                 p = new Node!(K, V)(spread(k.hashCode()), k, v, p);
//                 ++size;
//             }
//             else
//                 break;
//         }
//         if (size == 0L)
//             sizeCtl = 0;
//         else {
//             long ts = (long)(1.0 + size / LOAD_FACTOR);
//             int n = (ts >= (long)MAXIMUM_CAPACITY) ?
//                 MAXIMUM_CAPACITY : tableSizeFor((int)ts);
            
//             Node!(K, V)[] tab = (Node!(K, V)[])new Node<?,?>[n];
//             int mask = n - 1;
//             long added = 0L;
//             while (p != null) {
//                 boolean insertAtFront;
//                 Node!(K, V) next = p.next, first;
//                 int h = p.hash, j = h & mask;
//                 if ((first = tabAt(tab, j)) == null)
//                     insertAtFront = true;
//                 else {
//                     K k = p.key;
//                     if (first.hash < 0) {
//                         TreeBin!(K, V) t = (TreeBin!(K, V))first;
//                         if (t.putTreeVal(h, k, p.val) == null)
//                             ++added;
//                         insertAtFront = false;
//                     }
//                     else {
//                         int binCount = 0;
//                         insertAtFront = true;
//                         Node!(K, V) q; K qk;
//                         for (q = first; q != null; q = q.next) {
//                             if (q.hash == h &&
//                                 ((qk = q.key) == k ||
//                                  (qk != null && k.equals(qk)))) {
//                                 insertAtFront = false;
//                                 break;
//                             }
//                             ++binCount;
//                         }
//                         if (insertAtFront && binCount >= TREEIFY_THRESHOLD) {
//                             insertAtFront = false;
//                             ++added;
//                             p.next = first;
//                             TreeNode!(K, V) hd = null, tl = null;
//                             for (q = p; q != null; q = q.next) {
//                                 TreeNode!(K, V) t = new TreeNode!(K, V)
//                                     (q.hash, q.key, q.val, null, null);
//                                 if ((t.prev = tl) == null)
//                                     hd = t;
//                                 else
//                                     tl.next = t;
//                                 tl = t;
//                             }
//                             setTabAt(tab, j, new TreeBin!(K, V)(hd));
//                         }
//                     }
//                 }
//                 if (insertAtFront) {
//                     ++added;
//                     p.next = first;
//                     setTabAt(tab, j, p);
//                 }
//                 p = next;
//             }
//             table = tab;
//             sizeCtl = n - (n >>> 2);
//             baseCount = added;
//         }
//     }

//     // ConcurrentMap methods

//     /**
//      * {@inheritDoc}
//      *
//      * @return the previous value associated with the specified key,
//      *         or {@code null} if there was no mapping for the key
//      * @throws NullPointerException if the specified key or value is null
//      */
//     public V putIfAbsent(K key, V value) {
//         return putVal(key, value, true);
//     }

//     /**
//      * {@inheritDoc}
//      *
//      * @throws NullPointerException if the specified key is null
//      */
//     public boolean remove(Object key, Object value) {
//         if (key == null)
//             throw new NullPointerException();
//         return value != null && replaceNode(key, null, value) != null;
//     }

//     /**
//      * {@inheritDoc}
//      *
//      * @throws NullPointerException if any of the arguments are null
//      */
//     public boolean replace(K key, V oldValue, V newValue) {
//         if (key == null || oldValue == null || newValue == null)
//             throw new NullPointerException();
//         return replaceNode(key, newValue, oldValue) != null;
//     }

//     /**
//      * {@inheritDoc}
//      *
//      * @return the previous value associated with the specified key,
//      *         or {@code null} if there was no mapping for the key
//      * @throws NullPointerException if the specified key or value is null
//      */
//     public V replace(K key, V value) {
//         if (key == null || value == null)
//             throw new NullPointerException();
//         return replaceNode(key, value, null);
//     }

//     // Overrides of JDK8+ Map extension method defaults

//     /**
//      * Returns the value to which the specified key is mapped, or the
//      * given default value if this map contains no mapping for the
//      * key.
//      *
//      * @param key the key whose associated value is to be returned
//      * @param defaultValue the value to return if this map contains
//      * no mapping for the given key
//      * @return the mapping for the key, if present; else the default value
//      * @throws NullPointerException if the specified key is null
//      */
//     public V getOrDefault(Object key, V defaultValue) {
//         V v;
//         return (v = get(key)) == null ? defaultValue : v;
//     }

//     public void forEach(BiConsumer<? super K, ? super V> action) {
//         if (action == null) throw new NullPointerException();
//         Node!(K, V)[] t;
//         if ((t = table) != null) {
//             Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//             for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                 action.accept(p.key, p.val);
//             }
//         }
//     }

//     public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
//         if (function == null) throw new NullPointerException();
//         Node!(K, V)[] t;
//         if ((t = table) != null) {
//             Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//             for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                 V oldValue = p.val;
//                 for (K key = p.key;;) {
//                     V newValue = function.apply(key, oldValue);
//                     if (newValue == null)
//                         throw new NullPointerException();
//                     if (replaceNode(key, newValue, oldValue) != null ||
//                         (oldValue = get(key)) == null)
//                         break;
//                 }
//             }
//         }
//     }

//     /**
//      * Helper method for EntrySetView.removeIf.
//      */
//     boolean removeEntryIf(Predicate<? super Entry!(K, V)> function) {
//         if (function == null) throw new NullPointerException();
//         Node!(K, V)[] t;
//         boolean removed = false;
//         if ((t = table) != null) {
//             Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//             for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                 K k = p.key;
//                 V v = p.val;
//                 Map.Entry!(K, V) e = new AbstractMap.SimpleImmutableEntry<>(k, v);
//                 if (function.test(e) && replaceNode(k, null, v) != null)
//                     removed = true;
//             }
//         }
//         return removed;
//     }

//     /**
//      * Helper method for ValuesView.removeIf.
//      */
//     boolean removeValueIf(Predicate<? super V> function) {
//         if (function == null) throw new NullPointerException();
//         Node!(K, V)[] t;
//         boolean removed = false;
//         if ((t = table) != null) {
//             Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//             for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                 K k = p.key;
//                 V v = p.val;
//                 if (function.test(v) && replaceNode(k, null, v) != null)
//                     removed = true;
//             }
//         }
//         return removed;
//     }

//     /**
//      * If the specified key is not already associated with a value,
//      * attempts to compute its value using the given mapping function
//      * and enters it into this map unless {@code null}.  The entire
//      * method invocation is performed atomically, so the function is
//      * applied at most once per key.  Some attempted update operations
//      * on this map by other threads may be blocked while computation
//      * is in progress, so the computation should be short and simple,
//      * and must not attempt to update any other mappings of this map.
//      *
//      * @param key key with which the specified value is to be associated
//      * @param mappingFunction the function to compute a value
//      * @return the current (existing or computed) value associated with
//      *         the specified key, or null if the computed value is null
//      * @throws NullPointerException if the specified key or mappingFunction
//      *         is null
//      * @throws IllegalStateException if the computation detectably
//      *         attempts a recursive update to this map that would
//      *         otherwise never complete
//      * @throws RuntimeException or Error if the mappingFunction does so,
//      *         in which case the mapping is left unestablished
//      */
//     public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction) {
//         if (key == null || mappingFunction == null)
//             throw new NullPointerException();
//         int h = spread(key.hashCode());
//         V val = null;
//         int binCount = 0;
//         for (Node!(K, V)[] tab = table;;) {
//             Node!(K, V) f; int n, i, fh; K fk; V fv;
//             if (tab == null || (n = tab.length) == 0)
//                 tab = initTable();
//             else if ((f = tabAt(tab, i = (n - 1) & h)) == null) {
//                 Node!(K, V) r = new ReservationNode!(K, V)();
//                 synchronized (r) {
//                     if (casTabAt(tab, i, null, r)) {
//                         binCount = 1;
//                         Node!(K, V) node = null;
//                         try {
//                             if ((val = mappingFunction.apply(key)) != null)
//                                 node = new Node!(K, V)(h, key, val);
//                         } finally {
//                             setTabAt(tab, i, node);
//                         }
//                     }
//                 }
//                 if (binCount != 0)
//                     break;
//             }
//             else if ((fh = f.hash) == MOVED)
//                 tab = helpTransfer(tab, f);
//             else if (fh == h    // check first node without acquiring lock
//                      && ((fk = f.key) == key || (fk != null && key.equals(fk)))
//                      && (fv = f.val) != null)
//                 return fv;
//             else {
//                 boolean added = false;
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         if (fh >= 0) {
//                             binCount = 1;
//                             for (Node!(K, V) e = f;; ++binCount) {
//                                 K ek;
//                                 if (e.hash == h &&
//                                     ((ek = e.key) == key ||
//                                      (ek != null && key.equals(ek)))) {
//                                     val = e.val;
//                                     break;
//                                 }
//                                 Node!(K, V) pred = e;
//                                 if ((e = e.next) == null) {
//                                     if ((val = mappingFunction.apply(key)) != null) {
//                                         if (pred.next != null)
//                                             throw new IllegalStateException("Recursive update");
//                                         added = true;
//                                         pred.next = new Node!(K, V)(h, key, val);
//                                     }
//                                     break;
//                                 }
//                             }
//                         }
//                         else if (f instanceof TreeBin) {
//                             binCount = 2;
//                             TreeBin!(K, V) t = (TreeBin!(K, V))f;
//                             TreeNode!(K, V) r, p;
//                             if ((r = t.root) != null &&
//                                 (p = r.findTreeNode(h, key, null)) != null)
//                                 val = p.val;
//                             else if ((val = mappingFunction.apply(key)) != null) {
//                                 added = true;
//                                 t.putTreeVal(h, key, val);
//                             }
//                         }
//                         else if (f instanceof ReservationNode)
//                             throw new IllegalStateException("Recursive update");
//                     }
//                 }
//                 if (binCount != 0) {
//                     if (binCount >= TREEIFY_THRESHOLD)
//                         treeifyBin(tab, i);
//                     if (!added)
//                         return val;
//                     break;
//                 }
//             }
//         }
//         if (val != null)
//             addCount(1L, binCount);
//         return val;
//     }

//     /**
//      * If the value for the specified key is present, attempts to
//      * compute a new mapping given the key and its current mapped
//      * value.  The entire method invocation is performed atomically.
//      * Some attempted update operations on this map by other threads
//      * may be blocked while computation is in progress, so the
//      * computation should be short and simple, and must not attempt to
//      * update any other mappings of this map.
//      *
//      * @param key key with which a value may be associated
//      * @param remappingFunction the function to compute a value
//      * @return the new value associated with the specified key, or null if none
//      * @throws NullPointerException if the specified key or remappingFunction
//      *         is null
//      * @throws IllegalStateException if the computation detectably
//      *         attempts a recursive update to this map that would
//      *         otherwise never complete
//      * @throws RuntimeException or Error if the remappingFunction does so,
//      *         in which case the mapping is unchanged
//      */
//     public V computeIfPresent(K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
//         if (key == null || remappingFunction == null)
//             throw new NullPointerException();
//         int h = spread(key.hashCode());
//         V val = null;
//         int delta = 0;
//         int binCount = 0;
//         for (Node!(K, V)[] tab = table;;) {
//             Node!(K, V) f; int n, i, fh;
//             if (tab == null || (n = tab.length) == 0)
//                 tab = initTable();
//             else if ((f = tabAt(tab, i = (n - 1) & h)) == null)
//                 break;
//             else if ((fh = f.hash) == MOVED)
//                 tab = helpTransfer(tab, f);
//             else {
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         if (fh >= 0) {
//                             binCount = 1;
//                             for (Node!(K, V) e = f, pred = null;; ++binCount) {
//                                 K ek;
//                                 if (e.hash == h &&
//                                     ((ek = e.key) == key ||
//                                      (ek != null && key.equals(ek)))) {
//                                     val = remappingFunction.apply(key, e.val);
//                                     if (val != null)
//                                         e.val = val;
//                                     else {
//                                         delta = -1;
//                                         Node!(K, V) en = e.next;
//                                         if (pred != null)
//                                             pred.next = en;
//                                         else
//                                             setTabAt(tab, i, en);
//                                     }
//                                     break;
//                                 }
//                                 pred = e;
//                                 if ((e = e.next) == null)
//                                     break;
//                             }
//                         }
//                         else if (f instanceof TreeBin) {
//                             binCount = 2;
//                             TreeBin!(K, V) t = (TreeBin!(K, V))f;
//                             TreeNode!(K, V) r, p;
//                             if ((r = t.root) != null &&
//                                 (p = r.findTreeNode(h, key, null)) != null) {
//                                 val = remappingFunction.apply(key, p.val);
//                                 if (val != null)
//                                     p.val = val;
//                                 else {
//                                     delta = -1;
//                                     if (t.removeTreeNode(p))
//                                         setTabAt(tab, i, untreeify(t.first));
//                                 }
//                             }
//                         }
//                         else if (f instanceof ReservationNode)
//                             throw new IllegalStateException("Recursive update");
//                     }
//                 }
//                 if (binCount != 0)
//                     break;
//             }
//         }
//         if (delta != 0)
//             addCount((long)delta, binCount);
//         return val;
//     }

//     /**
//      * Attempts to compute a mapping for the specified key and its
//      * current mapped value (or {@code null} if there is no current
//      * mapping). The entire method invocation is performed atomically.
//      * Some attempted update operations on this map by other threads
//      * may be blocked while computation is in progress, so the
//      * computation should be short and simple, and must not attempt to
//      * update any other mappings of this Map.
//      *
//      * @param key key with which the specified value is to be associated
//      * @param remappingFunction the function to compute a value
//      * @return the new value associated with the specified key, or null if none
//      * @throws NullPointerException if the specified key or remappingFunction
//      *         is null
//      * @throws IllegalStateException if the computation detectably
//      *         attempts a recursive update to this map that would
//      *         otherwise never complete
//      * @throws RuntimeException or Error if the remappingFunction does so,
//      *         in which case the mapping is unchanged
//      */
//     public V compute(K key,
//                      BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
//         if (key == null || remappingFunction == null)
//             throw new NullPointerException();
//         int h = spread(key.hashCode());
//         V val = null;
//         int delta = 0;
//         int binCount = 0;
//         for (Node!(K, V)[] tab = table;;) {
//             Node!(K, V) f; int n, i, fh;
//             if (tab == null || (n = tab.length) == 0)
//                 tab = initTable();
//             else if ((f = tabAt(tab, i = (n - 1) & h)) == null) {
//                 Node!(K, V) r = new ReservationNode!(K, V)();
//                 synchronized (r) {
//                     if (casTabAt(tab, i, null, r)) {
//                         binCount = 1;
//                         Node!(K, V) node = null;
//                         try {
//                             if ((val = remappingFunction.apply(key, null)) != null) {
//                                 delta = 1;
//                                 node = new Node!(K, V)(h, key, val);
//                             }
//                         } finally {
//                             setTabAt(tab, i, node);
//                         }
//                     }
//                 }
//                 if (binCount != 0)
//                     break;
//             }
//             else if ((fh = f.hash) == MOVED)
//                 tab = helpTransfer(tab, f);
//             else {
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         if (fh >= 0) {
//                             binCount = 1;
//                             for (Node!(K, V) e = f, pred = null;; ++binCount) {
//                                 K ek;
//                                 if (e.hash == h &&
//                                     ((ek = e.key) == key ||
//                                      (ek != null && key.equals(ek)))) {
//                                     val = remappingFunction.apply(key, e.val);
//                                     if (val != null)
//                                         e.val = val;
//                                     else {
//                                         delta = -1;
//                                         Node!(K, V) en = e.next;
//                                         if (pred != null)
//                                             pred.next = en;
//                                         else
//                                             setTabAt(tab, i, en);
//                                     }
//                                     break;
//                                 }
//                                 pred = e;
//                                 if ((e = e.next) == null) {
//                                     val = remappingFunction.apply(key, null);
//                                     if (val != null) {
//                                         if (pred.next != null)
//                                             throw new IllegalStateException("Recursive update");
//                                         delta = 1;
//                                         pred.next = new Node!(K, V)(h, key, val);
//                                     }
//                                     break;
//                                 }
//                             }
//                         }
//                         else if (f instanceof TreeBin) {
//                             binCount = 1;
//                             TreeBin!(K, V) t = (TreeBin!(K, V))f;
//                             TreeNode!(K, V) r, p;
//                             if ((r = t.root) != null)
//                                 p = r.findTreeNode(h, key, null);
//                             else
//                                 p = null;
//                             V pv = (p == null) ? null : p.val;
//                             val = remappingFunction.apply(key, pv);
//                             if (val != null) {
//                                 if (p != null)
//                                     p.val = val;
//                                 else {
//                                     delta = 1;
//                                     t.putTreeVal(h, key, val);
//                                 }
//                             }
//                             else if (p != null) {
//                                 delta = -1;
//                                 if (t.removeTreeNode(p))
//                                     setTabAt(tab, i, untreeify(t.first));
//                             }
//                         }
//                         else if (f instanceof ReservationNode)
//                             throw new IllegalStateException("Recursive update");
//                     }
//                 }
//                 if (binCount != 0) {
//                     if (binCount >= TREEIFY_THRESHOLD)
//                         treeifyBin(tab, i);
//                     break;
//                 }
//             }
//         }
//         if (delta != 0)
//             addCount((long)delta, binCount);
//         return val;
//     }

//     /**
//      * If the specified key is not already associated with a
//      * (non-null) value, associates it with the given value.
//      * Otherwise, replaces the value with the results of the given
//      * remapping function, or removes if {@code null}. The entire
//      * method invocation is performed atomically.  Some attempted
//      * update operations on this map by other threads may be blocked
//      * while computation is in progress, so the computation should be
//      * short and simple, and must not attempt to update any other
//      * mappings of this Map.
//      *
//      * @param key key with which the specified value is to be associated
//      * @param value the value to use if absent
//      * @param remappingFunction the function to recompute a value if present
//      * @return the new value associated with the specified key, or null if none
//      * @throws NullPointerException if the specified key or the
//      *         remappingFunction is null
//      * @throws RuntimeException or Error if the remappingFunction does so,
//      *         in which case the mapping is unchanged
//      */
//     public V merge(K key, V value, BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
//         if (key == null || value == null || remappingFunction == null)
//             throw new NullPointerException();
//         int h = spread(key.hashCode());
//         V val = null;
//         int delta = 0;
//         int binCount = 0;
//         for (Node!(K, V)[] tab = table;;) {
//             Node!(K, V) f; int n, i, fh;
//             if (tab == null || (n = tab.length) == 0)
//                 tab = initTable();
//             else if ((f = tabAt(tab, i = (n - 1) & h)) == null) {
//                 if (casTabAt(tab, i, null, new Node!(K, V)(h, key, value))) {
//                     delta = 1;
//                     val = value;
//                     break;
//                 }
//             }
//             else if ((fh = f.hash) == MOVED)
//                 tab = helpTransfer(tab, f);
//             else {
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         if (fh >= 0) {
//                             binCount = 1;
//                             for (Node!(K, V) e = f, pred = null;; ++binCount) {
//                                 K ek;
//                                 if (e.hash == h &&
//                                     ((ek = e.key) == key ||
//                                      (ek != null && key.equals(ek)))) {
//                                     val = remappingFunction.apply(e.val, value);
//                                     if (val != null)
//                                         e.val = val;
//                                     else {
//                                         delta = -1;
//                                         Node!(K, V) en = e.next;
//                                         if (pred != null)
//                                             pred.next = en;
//                                         else
//                                             setTabAt(tab, i, en);
//                                     }
//                                     break;
//                                 }
//                                 pred = e;
//                                 if ((e = e.next) == null) {
//                                     delta = 1;
//                                     val = value;
//                                     pred.next = new Node!(K, V)(h, key, val);
//                                     break;
//                                 }
//                             }
//                         }
//                         else if (f instanceof TreeBin) {
//                             binCount = 2;
//                             TreeBin!(K, V) t = (TreeBin!(K, V))f;
//                             TreeNode!(K, V) r = t.root;
//                             TreeNode!(K, V) p = (r == null) ? null :
//                                 r.findTreeNode(h, key, null);
//                             val = (p == null) ? value :
//                                 remappingFunction.apply(p.val, value);
//                             if (val != null) {
//                                 if (p != null)
//                                     p.val = val;
//                                 else {
//                                     delta = 1;
//                                     t.putTreeVal(h, key, val);
//                                 }
//                             }
//                             else if (p != null) {
//                                 delta = -1;
//                                 if (t.removeTreeNode(p))
//                                     setTabAt(tab, i, untreeify(t.first));
//                             }
//                         }
//                         else if (f instanceof ReservationNode)
//                             throw new IllegalStateException("Recursive update");
//                     }
//                 }
//                 if (binCount != 0) {
//                     if (binCount >= TREEIFY_THRESHOLD)
//                         treeifyBin(tab, i);
//                     break;
//                 }
//             }
//         }
//         if (delta != 0)
//             addCount((long)delta, binCount);
//         return val;
//     }

//     // Hashtable legacy methods

//     /**
//      * Tests if some key maps into the specified value in this table.
//      *
//      * <p>Note that this method is identical in functionality to
//      * {@link #containsValue(Object)}, and exists solely to ensure
//      * full compatibility with class {@link java.util.Hashtable},
//      * which supported this method prior to introduction of the
//      * Java Collections Framework.
//      *
//      * @param  value a value to search for
//      * @return {@code true} if and only if some key maps to the
//      *         {@code value} argument in this table as
//      *         determined by the {@code equals} method;
//      *         {@code false} otherwise
//      * @throws NullPointerException if the specified value is null
//      */
//     public boolean contains(Object value) {
//         return containsValue(value);
//     }

//     /**
//      * Returns an enumeration of the keys in this table.
//      *
//      * @return an enumeration of the keys in this table
//      * @see #keySet()
//      */
//     public Enumeration<K> keys() {
//         Node!(K, V)[] t;
//         int f = (t = table) == null ? 0 : t.length;
//         return new KeyIterator!(K, V)(t, f, 0, f, this);
//     }

//     /**
//      * Returns an enumeration of the values in this table.
//      *
//      * @return an enumeration of the values in this table
//      * @see #values()
//      */
//     public Enumeration<V> elements() {
//         Node!(K, V)[] t;
//         int f = (t = table) == null ? 0 : t.length;
//         return new ValueIterator!(K, V)(t, f, 0, f, this);
//     }

//     // ConcurrentHashMap-only methods

//     /**
//      * Returns the number of mappings. This method should be used
//      * instead of {@link #size} because a ConcurrentHashMap may
//      * contain more mappings than can be represented as an int. The
//      * value returned is an estimate; the actual count may differ if
//      * there are concurrent insertions or removals.
//      *
//      * @return the number of mappings
//      */
//     public long mappingCount() {
//         long n = sumCount();
//         return (n < 0L) ? 0L : n; // ignore transient negative values
//     }

//     /**
//      * Creates a new {@link Set} backed by a ConcurrentHashMap
//      * from the given type to {@code Boolean.TRUE}.
//      *
//      * @param <K> the element type of the returned set
//      * @return the new set
//      */
//     public static <K> KeySetView<K,Boolean> newKeySet() {
//         return new KeySetView<K,Boolean>
//             (new ConcurrentHashMap<K,Boolean>(), Boolean.TRUE);
//     }

//     /**
//      * Creates a new {@link Set} backed by a ConcurrentHashMap
//      * from the given type to {@code Boolean.TRUE}.
//      *
//      * @param initialCapacity The implementation performs internal
//      * sizing to accommodate this many elements.
//      * @param <K> the element type of the returned set
//      * @return the new set
//      * @throws IllegalArgumentException if the initial capacity of
//      * elements is negative
//      */
//     public static <K> KeySetView<K,Boolean> newKeySet(int initialCapacity) {
//         return new KeySetView<K,Boolean>
//             (new ConcurrentHashMap<K,Boolean>(initialCapacity), Boolean.TRUE);
//     }

//     /**
//      * Returns a {@link Set} view of the keys in this map, using the
//      * given common mapped value for any additions (i.e., {@link
//      * Collection#add} and {@link Collection#addAll(Collection)}).
//      * This is of course only appropriate if it is acceptable to use
//      * the same value for all additions from this view.
//      *
//      * @param mappedValue the mapped value to use for any additions
//      * @return the set view
//      * @throws NullPointerException if the mappedValue is null
//      */
//     public KeySetView!(K, V) keySet(V mappedValue) {
//         if (mappedValue == null)
//             throw new NullPointerException();
//         return new KeySetView!(K, V)(this, mappedValue);
//     }

//     /* ---------------- Special Nodes -------------- */

//     /**
//      * A node inserted at head of bins during transfer operations.
//      */
//     static final class ForwardingNode!(K, V) extends Node!(K, V) {
//         final Node!(K, V)[] nextTable;
//         ForwardingNode(Node!(K, V)[] tab) {
//             super(MOVED, null, null);
//             this.nextTable = tab;
//         }

//         Node!(K, V) find(int h, Object k) {
//             // loop to avoid arbitrarily deep recursion on forwarding nodes
//             outer: for (Node!(K, V)[] tab = nextTable;;) {
//                 Node!(K, V) e; int n;
//                 if (k == null || tab == null || (n = tab.length) == 0 ||
//                     (e = tabAt(tab, (n - 1) & h)) == null)
//                     return null;
//                 for (;;) {
//                     int eh; K ek;
//                     if ((eh = e.hash) == h &&
//                         ((ek = e.key) == k || (ek != null && k.equals(ek))))
//                         return e;
//                     if (eh < 0) {
//                         if (e instanceof ForwardingNode) {
//                             tab = ((ForwardingNode!(K, V))e).nextTable;
//                             continue outer;
//                         }
//                         else
//                             return e.find(h, k);
//                     }
//                     if ((e = e.next) == null)
//                         return null;
//                 }
//             }
//         }
//     }

//     /**
//      * A place-holder node used in computeIfAbsent and compute.
//      */
//     static final class ReservationNode!(K, V) extends Node!(K, V) {
//         ReservationNode() {
//             super(RESERVED, null, null);
//         }

//         Node!(K, V) find(int h, Object k) {
//             return null;
//         }
//     }

//     /* ---------------- Table Initialization and Resizing -------------- */

//     /**
//      * Returns the stamp bits for resizing a table of size n.
//      * Must be negative when shifted left by RESIZE_STAMP_SHIFT.
//      */
//     static final int resizeStamp(int n) {
//         return Integer.numberOfLeadingZeros(n) | (1 << (RESIZE_STAMP_BITS - 1));
//     }

//     /**
//      * Initializes table, using the size recorded in sizeCtl.
//      */
//     private final Node!(K, V)[] initTable() {
//         Node!(K, V)[] tab; int sc;
//         while ((tab = table) == null || tab.length == 0) {
//             if ((sc = sizeCtl) < 0)
//                 Thread.yield(); // lost initialization race; just spin
//             else if (U.compareAndSetInt(this, SIZECTL, sc, -1)) {
//                 try {
//                     if ((tab = table) == null || tab.length == 0) {
//                         int n = (sc > 0) ? sc : DEFAULT_CAPACITY;
                        
//                         Node!(K, V)[] nt = (Node!(K, V)[])new Node<?,?>[n];
//                         table = tab = nt;
//                         sc = n - (n >>> 2);
//                     }
//                 } finally {
//                     sizeCtl = sc;
//                 }
//                 break;
//             }
//         }
//         return tab;
//     }

//     /**
//      * Adds to count, and if table is too small and not already
//      * resizing, initiates transfer. If already resizing, helps
//      * perform transfer if work is available.  Rechecks occupancy
//      * after a transfer to see if another resize is already needed
//      * because resizings are lagging additions.
//      *
//      * @param x the count to add
//      * @param check if <0, don't check resize, if <= 1 only check if uncontended
//      */
//     private final void addCount(long x, int check) {
//         CounterCell[] cs; long b, s;
//         if ((cs = counterCells) != null ||
//             !U.compareAndSetLong(this, BASECOUNT, b = baseCount, s = b + x)) {
//             CounterCell c; long v; int m;
//             boolean uncontended = true;
//             if (cs == null || (m = cs.length - 1) < 0 ||
//                 (c = cs[ThreadLocalRandom.getProbe() & m]) == null ||
//                 !(uncontended =
//                   U.compareAndSetLong(c, CELLVALUE, v = c.value, v + x))) {
//                 fullAddCount(x, uncontended);
//                 return;
//             }
//             if (check <= 1)
//                 return;
//             s = sumCount();
//         }
//         if (check >= 0) {
//             Node!(K, V)[] tab, nt; int n, sc;
//             while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
//                    (n = tab.length) < MAXIMUM_CAPACITY) {
//                 int rs = resizeStamp(n) << RESIZE_STAMP_SHIFT;
//                 if (sc < 0) {
//                     if (sc == rs + MAX_RESIZERS || sc == rs + 1 ||
//                         (nt = nextTable) == null || transferIndex <= 0)
//                         break;
//                     if (U.compareAndSetInt(this, SIZECTL, sc, sc + 1))
//                         transfer(tab, nt);
//                 }
//                 else if (U.compareAndSetInt(this, SIZECTL, sc, rs + 2))
//                     transfer(tab, null);
//                 s = sumCount();
//             }
//         }
//     }

//     /**
//      * Helps transfer if a resize is in progress.
//      */
//     final Node!(K, V)[] helpTransfer(Node!(K, V)[] tab, Node!(K, V) f) {
//         Node!(K, V)[] nextTab; int sc;
//         if (tab != null && (f instanceof ForwardingNode) &&
//             (nextTab = ((ForwardingNode!(K, V))f).nextTable) != null) {
//             int rs = resizeStamp(tab.length) << RESIZE_STAMP_SHIFT;
//             while (nextTab == nextTable && table == tab &&
//                    (sc = sizeCtl) < 0) {
//                 if (sc == rs + MAX_RESIZERS || sc == rs + 1 ||
//                     transferIndex <= 0)
//                     break;
//                 if (U.compareAndSetInt(this, SIZECTL, sc, sc + 1)) {
//                     transfer(tab, nextTab);
//                     break;
//                 }
//             }
//             return nextTab;
//         }
//         return table;
//     }

//     /**
//      * Tries to presize table to accommodate the given number of elements.
//      *
//      * @param size number of elements (doesn't need to be perfectly accurate)
//      */
//     private final void tryPresize(int size) {
//         int c = (size >= (MAXIMUM_CAPACITY >>> 1)) ? MAXIMUM_CAPACITY :
//             tableSizeFor(size + (size >>> 1) + 1);
//         int sc;
//         while ((sc = sizeCtl) >= 0) {
//             Node!(K, V)[] tab = table; int n;
//             if (tab == null || (n = tab.length) == 0) {
//                 n = (sc > c) ? sc : c;
//                 if (U.compareAndSetInt(this, SIZECTL, sc, -1)) {
//                     try {
//                         if (table == tab) {
                            
//                             Node!(K, V)[] nt = (Node!(K, V)[])new Node<?,?>[n];
//                             table = nt;
//                             sc = n - (n >>> 2);
//                         }
//                     } finally {
//                         sizeCtl = sc;
//                     }
//                 }
//             }
//             else if (c <= sc || n >= MAXIMUM_CAPACITY)
//                 break;
//             else if (tab == table) {
//                 int rs = resizeStamp(n);
//                 if (U.compareAndSetInt(this, SIZECTL, sc,
//                                         (rs << RESIZE_STAMP_SHIFT) + 2))
//                     transfer(tab, null);
//             }
//         }
//     }

//     /**
//      * Moves and/or copies the nodes in each bin to new table. See
//      * above for explanation.
//      */
//     private final void transfer(Node!(K, V)[] tab, Node!(K, V)[] nextTab) {
//         int n = tab.length, stride;
//         if ((stride = (NCPU > 1) ? (n >>> 3) / NCPU : n) < MIN_TRANSFER_STRIDE)
//             stride = MIN_TRANSFER_STRIDE; // subdivide range
//         if (nextTab == null) {            // initiating
//             try {
                
//                 Node!(K, V)[] nt = (Node!(K, V)[])new Node<?,?>[n << 1];
//                 nextTab = nt;
//             } catch (Throwable ex) {      // try to cope with OOME
//                 sizeCtl = Integer.MAX_VALUE;
//                 return;
//             }
//             nextTable = nextTab;
//             transferIndex = n;
//         }
//         int nextn = nextTab.length;
//         ForwardingNode!(K, V) fwd = new ForwardingNode!(K, V)(nextTab);
//         boolean advance = true;
//         boolean finishing = false; // to ensure sweep before committing nextTab
//         for (int i = 0, bound = 0;;) {
//             Node!(K, V) f; int fh;
//             while (advance) {
//                 int nextIndex, nextBound;
//                 if (--i >= bound || finishing)
//                     advance = false;
//                 else if ((nextIndex = transferIndex) <= 0) {
//                     i = -1;
//                     advance = false;
//                 }
//                 else if (U.compareAndSetInt
//                          (this, TRANSFERINDEX, nextIndex,
//                           nextBound = (nextIndex > stride ?
//                                        nextIndex - stride : 0))) {
//                     bound = nextBound;
//                     i = nextIndex - 1;
//                     advance = false;
//                 }
//             }
//             if (i < 0 || i >= n || i + n >= nextn) {
//                 int sc;
//                 if (finishing) {
//                     nextTable = null;
//                     table = nextTab;
//                     sizeCtl = (n << 1) - (n >>> 1);
//                     return;
//                 }
//                 if (U.compareAndSetInt(this, SIZECTL, sc = sizeCtl, sc - 1)) {
//                     if ((sc - 2) != resizeStamp(n) << RESIZE_STAMP_SHIFT)
//                         return;
//                     finishing = advance = true;
//                     i = n; // recheck before commit
//                 }
//             }
//             else if ((f = tabAt(tab, i)) == null)
//                 advance = casTabAt(tab, i, null, fwd);
//             else if ((fh = f.hash) == MOVED)
//                 advance = true; // already processed
//             else {
//                 synchronized (f) {
//                     if (tabAt(tab, i) == f) {
//                         Node!(K, V) ln, hn;
//                         if (fh >= 0) {
//                             int runBit = fh & n;
//                             Node!(K, V) lastRun = f;
//                             for (Node!(K, V) p = f.next; p != null; p = p.next) {
//                                 int b = p.hash & n;
//                                 if (b != runBit) {
//                                     runBit = b;
//                                     lastRun = p;
//                                 }
//                             }
//                             if (runBit == 0) {
//                                 ln = lastRun;
//                                 hn = null;
//                             }
//                             else {
//                                 hn = lastRun;
//                                 ln = null;
//                             }
//                             for (Node!(K, V) p = f; p != lastRun; p = p.next) {
//                                 int ph = p.hash; K pk = p.key; V pv = p.val;
//                                 if ((ph & n) == 0)
//                                     ln = new Node!(K, V)(ph, pk, pv, ln);
//                                 else
//                                     hn = new Node!(K, V)(ph, pk, pv, hn);
//                             }
//                             setTabAt(nextTab, i, ln);
//                             setTabAt(nextTab, i + n, hn);
//                             setTabAt(tab, i, fwd);
//                             advance = true;
//                         }
//                         else if (f instanceof TreeBin) {
//                             TreeBin!(K, V) t = (TreeBin!(K, V))f;
//                             TreeNode!(K, V) lo = null, loTail = null;
//                             TreeNode!(K, V) hi = null, hiTail = null;
//                             int lc = 0, hc = 0;
//                             for (Node!(K, V) e = t.first; e != null; e = e.next) {
//                                 int h = e.hash;
//                                 TreeNode!(K, V) p = new TreeNode!(K, V)
//                                     (h, e.key, e.val, null, null);
//                                 if ((h & n) == 0) {
//                                     if ((p.prev = loTail) == null)
//                                         lo = p;
//                                     else
//                                         loTail.next = p;
//                                     loTail = p;
//                                     ++lc;
//                                 }
//                                 else {
//                                     if ((p.prev = hiTail) == null)
//                                         hi = p;
//                                     else
//                                         hiTail.next = p;
//                                     hiTail = p;
//                                     ++hc;
//                                 }
//                             }
//                             ln = (lc <= UNTREEIFY_THRESHOLD) ? untreeify(lo) :
//                                 (hc != 0) ? new TreeBin!(K, V)(lo) : t;
//                             hn = (hc <= UNTREEIFY_THRESHOLD) ? untreeify(hi) :
//                                 (lc != 0) ? new TreeBin!(K, V)(hi) : t;
//                             setTabAt(nextTab, i, ln);
//                             setTabAt(nextTab, i + n, hn);
//                             setTabAt(tab, i, fwd);
//                             advance = true;
//                         }
//                         else if (f instanceof ReservationNode)
//                             throw new IllegalStateException("Recursive update");
//                     }
//                 }
//             }
//         }
//     }

//     /* ---------------- Counter support -------------- */

//     /**
//      * A padded cell for distributing counts.  Adapted from LongAdder
//      * and Striped64.  See their internal docs for explanation.
//      */
//     @jdk.internal.vm.annotation.Contended static final class CounterCell {
//         volatile long value;
//         CounterCell(long x) { value = x; }
//     }

//     final long sumCount() {
//         CounterCell[] cs = counterCells;
//         long sum = baseCount;
//         if (cs != null) {
//             for (CounterCell c : cs)
//                 if (c != null)
//                     sum += c.value;
//         }
//         return sum;
//     }

//     // See LongAdder version for explanation
//     private final void fullAddCount(long x, boolean wasUncontended) {
//         int h;
//         if ((h = ThreadLocalRandom.getProbe()) == 0) {
//             ThreadLocalRandom.localInit();      // force initialization
//             h = ThreadLocalRandom.getProbe();
//             wasUncontended = true;
//         }
//         boolean collide = false;                // True if last slot nonempty
//         for (;;) {
//             CounterCell[] cs; CounterCell c; int n; long v;
//             if ((cs = counterCells) != null && (n = cs.length) > 0) {
//                 if ((c = cs[(n - 1) & h]) == null) {
//                     if (cellsBusy == 0) {            // Try to attach new Cell
//                         CounterCell r = new CounterCell(x); // Optimistic create
//                         if (cellsBusy == 0 &&
//                             U.compareAndSetInt(this, CELLSBUSY, 0, 1)) {
//                             boolean created = false;
//                             try {               // Recheck under lock
//                                 CounterCell[] rs; int m, j;
//                                 if ((rs = counterCells) != null &&
//                                     (m = rs.length) > 0 &&
//                                     rs[j = (m - 1) & h] == null) {
//                                     rs[j] = r;
//                                     created = true;
//                                 }
//                             } finally {
//                                 cellsBusy = 0;
//                             }
//                             if (created)
//                                 break;
//                             continue;           // Slot is now non-empty
//                         }
//                     }
//                     collide = false;
//                 }
//                 else if (!wasUncontended)       // CAS already known to fail
//                     wasUncontended = true;      // Continue after rehash
//                 else if (U.compareAndSetLong(c, CELLVALUE, v = c.value, v + x))
//                     break;
//                 else if (counterCells != cs || n >= NCPU)
//                     collide = false;            // At max size or stale
//                 else if (!collide)
//                     collide = true;
//                 else if (cellsBusy == 0 &&
//                          U.compareAndSetInt(this, CELLSBUSY, 0, 1)) {
//                     try {
//                         if (counterCells == cs) // Expand table unless stale
//                             counterCells = Arrays.copyOf(cs, n << 1);
//                     } finally {
//                         cellsBusy = 0;
//                     }
//                     collide = false;
//                     continue;                   // Retry with expanded table
//                 }
//                 h = ThreadLocalRandom.advanceProbe(h);
//             }
//             else if (cellsBusy == 0 && counterCells == cs &&
//                      U.compareAndSetInt(this, CELLSBUSY, 0, 1)) {
//                 boolean init = false;
//                 try {                           // Initialize table
//                     if (counterCells == cs) {
//                         CounterCell[] rs = new CounterCell[2];
//                         rs[h & 1] = new CounterCell(x);
//                         counterCells = rs;
//                         init = true;
//                     }
//                 } finally {
//                     cellsBusy = 0;
//                 }
//                 if (init)
//                     break;
//             }
//             else if (U.compareAndSetLong(this, BASECOUNT, v = baseCount, v + x))
//                 break;                          // Fall back on using base
//         }
//     }

//     /* ---------------- Conversion from/to TreeBins -------------- */

//     /**
//      * Replaces all linked nodes in bin at given index unless table is
//      * too small, in which case resizes instead.
//      */
//     private final void treeifyBin(Node!(K, V)[] tab, int index) {
//         Node!(K, V) b; int n;
//         if (tab != null) {
//             if ((n = tab.length) < MIN_TREEIFY_CAPACITY)
//                 tryPresize(n << 1);
//             else if ((b = tabAt(tab, index)) != null && b.hash >= 0) {
//                 synchronized (b) {
//                     if (tabAt(tab, index) == b) {
//                         TreeNode!(K, V) hd = null, tl = null;
//                         for (Node!(K, V) e = b; e != null; e = e.next) {
//                             TreeNode!(K, V) p =
//                                 new TreeNode!(K, V)(e.hash, e.key, e.val,
//                                                   null, null);
//                             if ((p.prev = tl) == null)
//                                 hd = p;
//                             else
//                                 tl.next = p;
//                             tl = p;
//                         }
//                         setTabAt(tab, index, new TreeBin!(K, V)(hd));
//                     }
//                 }
//             }
//         }
//     }

//     /**
//      * Returns a list of non-TreeNodes replacing those in given list.
//      */
//     static !(K, V) Node!(K, V) untreeify(Node!(K, V) b) {
//         Node!(K, V) hd = null, tl = null;
//         for (Node!(K, V) q = b; q != null; q = q.next) {
//             Node!(K, V) p = new Node!(K, V)(q.hash, q.key, q.val);
//             if (tl == null)
//                 hd = p;
//             else
//                 tl.next = p;
//             tl = p;
//         }
//         return hd;
//     }

//     /* ---------------- TreeNodes -------------- */

//     /**
//      * Nodes for use in TreeBins.
//      */
//     static final class TreeNode!(K, V) extends Node!(K, V) {
//         TreeNode!(K, V) parent;  // red-black tree links
//         TreeNode!(K, V) left;
//         TreeNode!(K, V) right;
//         TreeNode!(K, V) prev;    // needed to unlink next upon deletion
//         boolean red;

//         TreeNode(int hash, K key, V val, Node!(K, V) next,
//                  TreeNode!(K, V) parent) {
//             super(hash, key, val, next);
//             this.parent = parent;
//         }

//         Node!(K, V) find(int h, Object k) {
//             return findTreeNode(h, k, null);
//         }

//         /**
//          * Returns the TreeNode (or null if not found) for the given key
//          * starting at given root.
//          */
//         final TreeNode!(K, V) findTreeNode(int h, Object k, Class<?> kc) {
//             if (k != null) {
//                 TreeNode!(K, V) p = this;
//                 do {
//                     int ph, dir; K pk; TreeNode!(K, V) q;
//                     TreeNode!(K, V) pl = p.left, pr = p.right;
//                     if ((ph = p.hash) > h)
//                         p = pl;
//                     else if (ph < h)
//                         p = pr;
//                     else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
//                         return p;
//                     else if (pl == null)
//                         p = pr;
//                     else if (pr == null)
//                         p = pl;
//                     else if ((kc != null ||
//                               (kc = comparableClassFor(k)) != null) &&
//                              (dir = compareComparables(kc, k, pk)) != 0)
//                         p = (dir < 0) ? pl : pr;
//                     else if ((q = pr.findTreeNode(h, k, kc)) != null)
//                         return q;
//                     else
//                         p = pl;
//                 } while (p != null);
//             }
//             return null;
//         }
//     }

//     /* ---------------- TreeBins -------------- */

//     /**
//      * TreeNodes used at the heads of bins. TreeBins do not hold user
//      * keys or values, but instead point to list of TreeNodes and
//      * their root. They also maintain a parasitic read-write lock
//      * forcing writers (who hold bin lock) to wait for readers (who do
//      * not) to complete before tree restructuring operations.
//      */
//     static final class TreeBin!(K, V) extends Node!(K, V) {
//         TreeNode!(K, V) root;
//         volatile TreeNode!(K, V) first;
//         volatile Thread waiter;
//         volatile int lockState;
//         // values for lockState
//         static final int WRITER = 1; // set while holding write lock
//         static final int WAITER = 2; // set when waiting for write lock
//         static final int READER = 4; // increment value for setting read lock

//         /**
//          * Tie-breaking utility for ordering insertions when equal
//          * hashCodes and non-comparable. We don't require a total
//          * order, just a consistent insertion rule to maintain
//          * equivalence across rebalancings. Tie-breaking further than
//          * necessary simplifies testing a bit.
//          */
//         static int tieBreakOrder(Object a, Object b) {
//             int d;
//             if (a == null || b == null ||
//                 (d = a.getClass().getName().
//                  compareTo(b.getClass().getName())) == 0)
//                 d = (System.identityHashCode(a) <= System.identityHashCode(b) ?
//                      -1 : 1);
//             return d;
//         }

//         /**
//          * Creates bin with initial set of nodes headed by b.
//          */
//         TreeBin(TreeNode!(K, V) b) {
//             super(TREEBIN, null, null);
//             this.first = b;
//             TreeNode!(K, V) r = null;
//             for (TreeNode!(K, V) x = b, next; x != null; x = next) {
//                 next = (TreeNode!(K, V))x.next;
//                 x.left = x.right = null;
//                 if (r == null) {
//                     x.parent = null;
//                     x.red = false;
//                     r = x;
//                 }
//                 else {
//                     K k = x.key;
//                     int h = x.hash;
//                     Class<?> kc = null;
//                     for (TreeNode!(K, V) p = r;;) {
//                         int dir, ph;
//                         K pk = p.key;
//                         if ((ph = p.hash) > h)
//                             dir = -1;
//                         else if (ph < h)
//                             dir = 1;
//                         else if ((kc == null &&
//                                   (kc = comparableClassFor(k)) == null) ||
//                                  (dir = compareComparables(kc, k, pk)) == 0)
//                             dir = tieBreakOrder(k, pk);
//                         TreeNode!(K, V) xp = p;
//                         if ((p = (dir <= 0) ? p.left : p.right) == null) {
//                             x.parent = xp;
//                             if (dir <= 0)
//                                 xp.left = x;
//                             else
//                                 xp.right = x;
//                             r = balanceInsertion(r, x);
//                             break;
//                         }
//                     }
//                 }
//             }
//             this.root = r;
//             assert checkInvariants(root);
//         }

//         /**
//          * Acquires write lock for tree restructuring.
//          */
//         private final void lockRoot() {
//             if (!U.compareAndSetInt(this, LOCKSTATE, 0, WRITER))
//                 contendedLock(); // offload to separate method
//         }

//         /**
//          * Releases write lock for tree restructuring.
//          */
//         private final void unlockRoot() {
//             lockState = 0;
//         }

//         /**
//          * Possibly blocks awaiting root lock.
//          */
//         private final void contendedLock() {
//             boolean waiting = false;
//             for (int s;;) {
//                 if (((s = lockState) & ~WAITER) == 0) {
//                     if (U.compareAndSetInt(this, LOCKSTATE, s, WRITER)) {
//                         if (waiting)
//                             waiter = null;
//                         return;
//                     }
//                 }
//                 else if ((s & WAITER) == 0) {
//                     if (U.compareAndSetInt(this, LOCKSTATE, s, s | WAITER)) {
//                         waiting = true;
//                         waiter = Thread.currentThread();
//                     }
//                 }
//                 else if (waiting)
//                     LockSupport.park(this);
//             }
//         }

//         /**
//          * Returns matching node or null if none. Tries to search
//          * using tree comparisons from root, but continues linear
//          * search when lock not available.
//          */
//         final Node!(K, V) find(int h, Object k) {
//             if (k != null) {
//                 for (Node!(K, V) e = first; e != null; ) {
//                     int s; K ek;
//                     if (((s = lockState) & (WAITER|WRITER)) != 0) {
//                         if (e.hash == h &&
//                             ((ek = e.key) == k || (ek != null && k.equals(ek))))
//                             return e;
//                         e = e.next;
//                     }
//                     else if (U.compareAndSetInt(this, LOCKSTATE, s,
//                                                  s + READER)) {
//                         TreeNode!(K, V) r, p;
//                         try {
//                             p = ((r = root) == null ? null :
//                                  r.findTreeNode(h, k, null));
//                         } finally {
//                             Thread w;
//                             if (U.getAndAddInt(this, LOCKSTATE, -READER) ==
//                                 (READER|WAITER) && (w = waiter) != null)
//                                 LockSupport.unpark(w);
//                         }
//                         return p;
//                     }
//                 }
//             }
//             return null;
//         }

//         /**
//          * Finds or adds a node.
//          * @return null if added
//          */
//         final TreeNode!(K, V) putTreeVal(int h, K k, V v) {
//             Class<?> kc = null;
//             boolean searched = false;
//             for (TreeNode!(K, V) p = root;;) {
//                 int dir, ph; K pk;
//                 if (p == null) {
//                     first = root = new TreeNode!(K, V)(h, k, v, null, null);
//                     break;
//                 }
//                 else if ((ph = p.hash) > h)
//                     dir = -1;
//                 else if (ph < h)
//                     dir = 1;
//                 else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
//                     return p;
//                 else if ((kc == null &&
//                           (kc = comparableClassFor(k)) == null) ||
//                          (dir = compareComparables(kc, k, pk)) == 0) {
//                     if (!searched) {
//                         TreeNode!(K, V) q, ch;
//                         searched = true;
//                         if (((ch = p.left) != null &&
//                              (q = ch.findTreeNode(h, k, kc)) != null) ||
//                             ((ch = p.right) != null &&
//                              (q = ch.findTreeNode(h, k, kc)) != null))
//                             return q;
//                     }
//                     dir = tieBreakOrder(k, pk);
//                 }

//                 TreeNode!(K, V) xp = p;
//                 if ((p = (dir <= 0) ? p.left : p.right) == null) {
//                     TreeNode!(K, V) x, f = first;
//                     first = x = new TreeNode!(K, V)(h, k, v, f, xp);
//                     if (f != null)
//                         f.prev = x;
//                     if (dir <= 0)
//                         xp.left = x;
//                     else
//                         xp.right = x;
//                     if (!xp.red)
//                         x.red = true;
//                     else {
//                         lockRoot();
//                         try {
//                             root = balanceInsertion(root, x);
//                         } finally {
//                             unlockRoot();
//                         }
//                     }
//                     break;
//                 }
//             }
//             assert checkInvariants(root);
//             return null;
//         }

//         /**
//          * Removes the given node, that must be present before this
//          * call.  This is messier than typical red-black deletion code
//          * because we cannot swap the contents of an interior node
//          * with a leaf successor that is pinned by "next" pointers
//          * that are accessible independently of lock. So instead we
//          * swap the tree linkages.
//          *
//          * @return true if now too small, so should be untreeified
//          */
//         final boolean removeTreeNode(TreeNode!(K, V) p) {
//             TreeNode!(K, V) next = (TreeNode!(K, V))p.next;
//             TreeNode!(K, V) pred = p.prev;  // unlink traversal pointers
//             TreeNode!(K, V) r, rl;
//             if (pred == null)
//                 first = next;
//             else
//                 pred.next = next;
//             if (next != null)
//                 next.prev = pred;
//             if (first == null) {
//                 root = null;
//                 return true;
//             }
//             if ((r = root) == null || r.right == null || // too small
//                 (rl = r.left) == null || rl.left == null)
//                 return true;
//             lockRoot();
//             try {
//                 TreeNode!(K, V) replacement;
//                 TreeNode!(K, V) pl = p.left;
//                 TreeNode!(K, V) pr = p.right;
//                 if (pl != null && pr != null) {
//                     TreeNode!(K, V) s = pr, sl;
//                     while ((sl = s.left) != null) // find successor
//                         s = sl;
//                     boolean c = s.red; s.red = p.red; p.red = c; // swap colors
//                     TreeNode!(K, V) sr = s.right;
//                     TreeNode!(K, V) pp = p.parent;
//                     if (s == pr) { // p was s's direct parent
//                         p.parent = s;
//                         s.right = p;
//                     }
//                     else {
//                         TreeNode!(K, V) sp = s.parent;
//                         if ((p.parent = sp) != null) {
//                             if (s == sp.left)
//                                 sp.left = p;
//                             else
//                                 sp.right = p;
//                         }
//                         if ((s.right = pr) != null)
//                             pr.parent = s;
//                     }
//                     p.left = null;
//                     if ((p.right = sr) != null)
//                         sr.parent = p;
//                     if ((s.left = pl) != null)
//                         pl.parent = s;
//                     if ((s.parent = pp) == null)
//                         r = s;
//                     else if (p == pp.left)
//                         pp.left = s;
//                     else
//                         pp.right = s;
//                     if (sr != null)
//                         replacement = sr;
//                     else
//                         replacement = p;
//                 }
//                 else if (pl != null)
//                     replacement = pl;
//                 else if (pr != null)
//                     replacement = pr;
//                 else
//                     replacement = p;
//                 if (replacement != p) {
//                     TreeNode!(K, V) pp = replacement.parent = p.parent;
//                     if (pp == null)
//                         r = replacement;
//                     else if (p == pp.left)
//                         pp.left = replacement;
//                     else
//                         pp.right = replacement;
//                     p.left = p.right = p.parent = null;
//                 }

//                 root = (p.red) ? r : balanceDeletion(r, replacement);

//                 if (p == replacement) {  // detach pointers
//                     TreeNode!(K, V) pp;
//                     if ((pp = p.parent) != null) {
//                         if (p == pp.left)
//                             pp.left = null;
//                         else if (p == pp.right)
//                             pp.right = null;
//                         p.parent = null;
//                     }
//                 }
//             } finally {
//                 unlockRoot();
//             }
//             assert checkInvariants(root);
//             return false;
//         }

//         /* ------------------------------------------------------------ */
//         // Red-black tree methods, all adapted from CLR

//         static !(K, V) TreeNode!(K, V) rotateLeft(TreeNode!(K, V) root,
//                                               TreeNode!(K, V) p) {
//             TreeNode!(K, V) r, pp, rl;
//             if (p != null && (r = p.right) != null) {
//                 if ((rl = p.right = r.left) != null)
//                     rl.parent = p;
//                 if ((pp = r.parent = p.parent) == null)
//                     (root = r).red = false;
//                 else if (pp.left == p)
//                     pp.left = r;
//                 else
//                     pp.right = r;
//                 r.left = p;
//                 p.parent = r;
//             }
//             return root;
//         }

//         static !(K, V) TreeNode!(K, V) rotateRight(TreeNode!(K, V) root,
//                                                TreeNode!(K, V) p) {
//             TreeNode!(K, V) l, pp, lr;
//             if (p != null && (l = p.left) != null) {
//                 if ((lr = p.left = l.right) != null)
//                     lr.parent = p;
//                 if ((pp = l.parent = p.parent) == null)
//                     (root = l).red = false;
//                 else if (pp.right == p)
//                     pp.right = l;
//                 else
//                     pp.left = l;
//                 l.right = p;
//                 p.parent = l;
//             }
//             return root;
//         }

//         static !(K, V) TreeNode!(K, V) balanceInsertion(TreeNode!(K, V) root,
//                                                     TreeNode!(K, V) x) {
//             x.red = true;
//             for (TreeNode!(K, V) xp, xpp, xppl, xppr;;) {
//                 if ((xp = x.parent) == null) {
//                     x.red = false;
//                     return x;
//                 }
//                 else if (!xp.red || (xpp = xp.parent) == null)
//                     return root;
//                 if (xp == (xppl = xpp.left)) {
//                     if ((xppr = xpp.right) != null && xppr.red) {
//                         xppr.red = false;
//                         xp.red = false;
//                         xpp.red = true;
//                         x = xpp;
//                     }
//                     else {
//                         if (x == xp.right) {
//                             root = rotateLeft(root, x = xp);
//                             xpp = (xp = x.parent) == null ? null : xp.parent;
//                         }
//                         if (xp != null) {
//                             xp.red = false;
//                             if (xpp != null) {
//                                 xpp.red = true;
//                                 root = rotateRight(root, xpp);
//                             }
//                         }
//                     }
//                 }
//                 else {
//                     if (xppl != null && xppl.red) {
//                         xppl.red = false;
//                         xp.red = false;
//                         xpp.red = true;
//                         x = xpp;
//                     }
//                     else {
//                         if (x == xp.left) {
//                             root = rotateRight(root, x = xp);
//                             xpp = (xp = x.parent) == null ? null : xp.parent;
//                         }
//                         if (xp != null) {
//                             xp.red = false;
//                             if (xpp != null) {
//                                 xpp.red = true;
//                                 root = rotateLeft(root, xpp);
//                             }
//                         }
//                     }
//                 }
//             }
//         }

//         static !(K, V) TreeNode!(K, V) balanceDeletion(TreeNode!(K, V) root,
//                                                    TreeNode!(K, V) x) {
//             for (TreeNode!(K, V) xp, xpl, xpr;;) {
//                 if (x == null || x == root)
//                     return root;
//                 else if ((xp = x.parent) == null) {
//                     x.red = false;
//                     return x;
//                 }
//                 else if (x.red) {
//                     x.red = false;
//                     return root;
//                 }
//                 else if ((xpl = xp.left) == x) {
//                     if ((xpr = xp.right) != null && xpr.red) {
//                         xpr.red = false;
//                         xp.red = true;
//                         root = rotateLeft(root, xp);
//                         xpr = (xp = x.parent) == null ? null : xp.right;
//                     }
//                     if (xpr == null)
//                         x = xp;
//                     else {
//                         TreeNode!(K, V) sl = xpr.left, sr = xpr.right;
//                         if ((sr == null || !sr.red) &&
//                             (sl == null || !sl.red)) {
//                             xpr.red = true;
//                             x = xp;
//                         }
//                         else {
//                             if (sr == null || !sr.red) {
//                                 if (sl != null)
//                                     sl.red = false;
//                                 xpr.red = true;
//                                 root = rotateRight(root, xpr);
//                                 xpr = (xp = x.parent) == null ?
//                                     null : xp.right;
//                             }
//                             if (xpr != null) {
//                                 xpr.red = (xp == null) ? false : xp.red;
//                                 if ((sr = xpr.right) != null)
//                                     sr.red = false;
//                             }
//                             if (xp != null) {
//                                 xp.red = false;
//                                 root = rotateLeft(root, xp);
//                             }
//                             x = root;
//                         }
//                     }
//                 }
//                 else { // symmetric
//                     if (xpl != null && xpl.red) {
//                         xpl.red = false;
//                         xp.red = true;
//                         root = rotateRight(root, xp);
//                         xpl = (xp = x.parent) == null ? null : xp.left;
//                     }
//                     if (xpl == null)
//                         x = xp;
//                     else {
//                         TreeNode!(K, V) sl = xpl.left, sr = xpl.right;
//                         if ((sl == null || !sl.red) &&
//                             (sr == null || !sr.red)) {
//                             xpl.red = true;
//                             x = xp;
//                         }
//                         else {
//                             if (sl == null || !sl.red) {
//                                 if (sr != null)
//                                     sr.red = false;
//                                 xpl.red = true;
//                                 root = rotateLeft(root, xpl);
//                                 xpl = (xp = x.parent) == null ?
//                                     null : xp.left;
//                             }
//                             if (xpl != null) {
//                                 xpl.red = (xp == null) ? false : xp.red;
//                                 if ((sl = xpl.left) != null)
//                                     sl.red = false;
//                             }
//                             if (xp != null) {
//                                 xp.red = false;
//                                 root = rotateRight(root, xp);
//                             }
//                             x = root;
//                         }
//                     }
//                 }
//             }
//         }

//         /**
//          * Checks invariants recursively for the tree of Nodes rooted at t.
//          */
//         static !(K, V) boolean checkInvariants(TreeNode!(K, V) t) {
//             TreeNode!(K, V) tp = t.parent, tl = t.left, tr = t.right,
//                 tb = t.prev, tn = (TreeNode!(K, V))t.next;
//             if (tb != null && tb.next != t)
//                 return false;
//             if (tn != null && tn.prev != t)
//                 return false;
//             if (tp != null && t != tp.left && t != tp.right)
//                 return false;
//             if (tl != null && (tl.parent != t || tl.hash > t.hash))
//                 return false;
//             if (tr != null && (tr.parent != t || tr.hash < t.hash))
//                 return false;
//             if (t.red && tl != null && tl.red && tr != null && tr.red)
//                 return false;
//             if (tl != null && !checkInvariants(tl))
//                 return false;
//             if (tr != null && !checkInvariants(tr))
//                 return false;
//             return true;
//         }

//         private static final long LOCKSTATE = U.objectFieldOffset(
//             TreeBin.class, "lockState");
//     }

//     /* ----------------Table Traversal -------------- */

//     /**
//      * Records the table, its length, and current traversal index for a
//      * traverser that must process a region of a forwarded table before
//      * proceeding with current table.
//      */
//     static final class TableStack!(K, V) {
//         int length;
//         int index;
//         Node!(K, V)[] tab;
//         TableStack!(K, V) next;
//     }

//     /**
//      * Encapsulates traversal for methods such as containsValue; also
//      * serves as a base class for other iterators and spliterators.
//      *
//      * Method advance visits once each still-valid node that was
//      * reachable upon iterator construction. It might miss some that
//      * were added to a bin after the bin was visited, which is OK wrt
//      * consistency guarantees. Maintaining this property in the face
//      * of possible ongoing resizes requires a fair amount of
//      * bookkeeping state that is difficult to optimize away amidst
//      * volatile accesses.  Even so, traversal maintains reasonable
//      * throughput.
//      *
//      * Normally, iteration proceeds bin-by-bin traversing lists.
//      * However, if the table has been resized, then all future steps
//      * must traverse both the bin at the current index as well as at
//      * (index + baseSize); and so on for further resizings. To
//      * paranoically cope with potential sharing by users of iterators
//      * across threads, iteration terminates if a bounds checks fails
//      * for a table read.
//      */
//     static class Traverser!(K, V) {
//         Node!(K, V)[] tab;        // current table; updated if resized
//         Node!(K, V) next;         // the next entry to use
//         TableStack!(K, V) stack, spare; // to save/restore on ForwardingNodes
//         int index;              // index of bin to use next
//         int baseIndex;          // current index of initial table
//         int baseLimit;          // index bound for initial table
//         final int baseSize;     // initial table size

//         Traverser(Node!(K, V)[] tab, int size, int index, int limit) {
//             this.tab = tab;
//             this.baseSize = size;
//             this.baseIndex = this.index = index;
//             this.baseLimit = limit;
//             this.next = null;
//         }

//         /**
//          * Advances if possible, returning next valid node, or null if none.
//          */
//         final Node!(K, V) advance() {
//             Node!(K, V) e;
//             if ((e = next) != null)
//                 e = e.next;
//             for (;;) {
//                 Node!(K, V)[] t; int i, n;  // must use locals in checks
//                 if (e != null)
//                     return next = e;
//                 if (baseIndex >= baseLimit || (t = tab) == null ||
//                     (n = t.length) <= (i = index) || i < 0)
//                     return next = null;
//                 if ((e = tabAt(t, i)) != null && e.hash < 0) {
//                     if (e instanceof ForwardingNode) {
//                         tab = ((ForwardingNode!(K, V))e).nextTable;
//                         e = null;
//                         pushState(t, i, n);
//                         continue;
//                     }
//                     else if (e instanceof TreeBin)
//                         e = ((TreeBin!(K, V))e).first;
//                     else
//                         e = null;
//                 }
//                 if (stack != null)
//                     recoverState(n);
//                 else if ((index = i + baseSize) >= n)
//                     index = ++baseIndex; // visit upper slots if present
//             }
//         }

//         /**
//          * Saves traversal state upon encountering a forwarding node.
//          */
//         private void pushState(Node!(K, V)[] t, int i, int n) {
//             TableStack!(K, V) s = spare;  // reuse if possible
//             if (s != null)
//                 spare = s.next;
//             else
//                 s = new TableStack!(K, V)();
//             s.tab = t;
//             s.length = n;
//             s.index = i;
//             s.next = stack;
//             stack = s;
//         }

//         /**
//          * Possibly pops traversal state.
//          *
//          * @param n length of current table
//          */
//         private void recoverState(int n) {
//             TableStack!(K, V) s; int len;
//             while ((s = stack) != null && (index += (len = s.length)) >= n) {
//                 n = len;
//                 index = s.index;
//                 tab = s.tab;
//                 s.tab = null;
//                 TableStack!(K, V) next = s.next;
//                 s.next = spare; // save for reuse
//                 stack = next;
//                 spare = s;
//             }
//             if (s == null && (index += baseSize) >= n)
//                 index = ++baseIndex;
//         }
//     }

//     /**
//      * Base of key, value, and entry Iterators. Adds fields to
//      * Traverser to support iterator.remove.
//      */
//     static class BaseIterator!(K, V) extends Traverser!(K, V) {
//         final ConcurrentHashMap!(K, V) map;
//         Node!(K, V) lastReturned;
//         BaseIterator(Node!(K, V)[] tab, int size, int index, int limit,
//                     ConcurrentHashMap!(K, V) map) {
//             super(tab, size, index, limit);
//             this.map = map;
//             advance();
//         }

//         public final boolean hasNext() { return next != null; }
//         public final boolean hasMoreElements() { return next != null; }

//         public final void remove() {
//             Node!(K, V) p;
//             if ((p = lastReturned) == null)
//                 throw new IllegalStateException();
//             lastReturned = null;
//             map.replaceNode(p.key, null, null);
//         }
//     }

//     static final class KeyIterator!(K, V) extends BaseIterator!(K, V)
//         implements Iterator<K>, Enumeration<K> {
//         KeyIterator(Node!(K, V)[] tab, int size, int index, int limit,
//                     ConcurrentHashMap!(K, V) map) {
//             super(tab, size, index, limit, map);
//         }

//         public final K next() {
//             Node!(K, V) p;
//             if ((p = next) == null)
//                 throw new NoSuchElementException();
//             K k = p.key;
//             lastReturned = p;
//             advance();
//             return k;
//         }

//         public final K nextElement() { return next(); }
//     }

//     static final class ValueIterator!(K, V) extends BaseIterator!(K, V)
//         implements Iterator<V>, Enumeration<V> {
//         ValueIterator(Node!(K, V)[] tab, int size, int index, int limit,
//                       ConcurrentHashMap!(K, V) map) {
//             super(tab, size, index, limit, map);
//         }

//         public final V next() {
//             Node!(K, V) p;
//             if ((p = next) == null)
//                 throw new NoSuchElementException();
//             V v = p.val;
//             lastReturned = p;
//             advance();
//             return v;
//         }

//         public final V nextElement() { return next(); }
//     }

//     static final class EntryIterator!(K, V) extends BaseIterator!(K, V)
//         implements Iterator<Map.Entry!(K, V)> {
//         EntryIterator(Node!(K, V)[] tab, int size, int index, int limit,
//                       ConcurrentHashMap!(K, V) map) {
//             super(tab, size, index, limit, map);
//         }

//         public final Map.Entry!(K, V) next() {
//             Node!(K, V) p;
//             if ((p = next) == null)
//                 throw new NoSuchElementException();
//             K k = p.key;
//             V v = p.val;
//             lastReturned = p;
//             advance();
//             return new MapEntry!(K, V)(k, v, map);
//         }
//     }

//     /**
//      * Exported Entry for EntryIterator.
//      */
//     static final class MapEntry!(K, V) implements Map.Entry!(K, V) {
//         final K key; // non-null
//         V val;       // non-null
//         final ConcurrentHashMap!(K, V) map;
//         MapEntry(K key, V val, ConcurrentHashMap!(K, V) map) {
//             this.key = key;
//             this.val = val;
//             this.map = map;
//         }
//         public K getKey()        { return key; }
//         public V getValue()      { return val; }
//         public int hashCode()    { return key.hashCode() ^ val.hashCode(); }
//         public String toString() {
//             return Helpers.mapEntryToString(key, val);
//         }

//         public boolean equals(Object o) {
//             Object k, v; Map.Entry<?,?> e;
//             return ((o instanceof Map.Entry) &&
//                     (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
//                     (v = e.getValue()) != null &&
//                     (k == key || k.equals(key)) &&
//                     (v == val || v.equals(val)));
//         }

//         /**
//          * Sets our entry's value and writes through to the map. The
//          * value to return is somewhat arbitrary here. Since we do not
//          * necessarily track asynchronous changes, the most recent
//          * "previous" value could be different from what we return (or
//          * could even have been removed, in which case the put will
//          * re-establish). We do not and cannot guarantee more.
//          */
//         public V setValue(V value) {
//             if (value == null) throw new NullPointerException();
//             V v = val;
//             val = value;
//             map.put(key, value);
//             return v;
//         }
//     }

//     static final class KeySpliterator!(K, V) extends Traverser!(K, V)
//         implements Spliterator<K> {
//         long est;               // size estimate
//         KeySpliterator(Node!(K, V)[] tab, int size, int index, int limit,
//                        long est) {
//             super(tab, size, index, limit);
//             this.est = est;
//         }

//         public KeySpliterator!(K, V) trySplit() {
//             int i, f, h;
//             return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
//                 new KeySpliterator!(K, V)(tab, baseSize, baseLimit = h,
//                                         f, est >>>= 1);
//         }

//         public void forEachRemaining(Consumer<? super K> action) {
//             if (action == null) throw new NullPointerException();
//             for (Node!(K, V) p; (p = advance()) != null;)
//                 action.accept(p.key);
//         }

//         public boolean tryAdvance(Consumer<? super K> action) {
//             if (action == null) throw new NullPointerException();
//             Node!(K, V) p;
//             if ((p = advance()) == null)
//                 return false;
//             action.accept(p.key);
//             return true;
//         }

//         public long estimateSize() { return est; }

//         public int characteristics() {
//             return Spliterator.DISTINCT | Spliterator.CONCURRENT |
//                 Spliterator.NONNULL;
//         }
//     }

//     static final class ValueSpliterator!(K, V) extends Traverser!(K, V)
//         implements Spliterator<V> {
//         long est;               // size estimate
//         ValueSpliterator(Node!(K, V)[] tab, int size, int index, int limit,
//                          long est) {
//             super(tab, size, index, limit);
//             this.est = est;
//         }

//         public ValueSpliterator!(K, V) trySplit() {
//             int i, f, h;
//             return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
//                 new ValueSpliterator!(K, V)(tab, baseSize, baseLimit = h,
//                                           f, est >>>= 1);
//         }

//         public void forEachRemaining(Consumer<? super V> action) {
//             if (action == null) throw new NullPointerException();
//             for (Node!(K, V) p; (p = advance()) != null;)
//                 action.accept(p.val);
//         }

//         public boolean tryAdvance(Consumer<? super V> action) {
//             if (action == null) throw new NullPointerException();
//             Node!(K, V) p;
//             if ((p = advance()) == null)
//                 return false;
//             action.accept(p.val);
//             return true;
//         }

//         public long estimateSize() { return est; }

//         public int characteristics() {
//             return Spliterator.CONCURRENT | Spliterator.NONNULL;
//         }
//     }

//     static final class EntrySpliterator!(K, V) extends Traverser!(K, V)
//         implements Spliterator<Map.Entry!(K, V)> {
//         final ConcurrentHashMap!(K, V) map; // To export MapEntry
//         long est;               // size estimate
//         EntrySpliterator(Node!(K, V)[] tab, int size, int index, int limit,
//                          long est, ConcurrentHashMap!(K, V) map) {
//             super(tab, size, index, limit);
//             this.map = map;
//             this.est = est;
//         }

//         public EntrySpliterator!(K, V) trySplit() {
//             int i, f, h;
//             return (h = ((i = baseIndex) + (f = baseLimit)) >>> 1) <= i ? null :
//                 new EntrySpliterator!(K, V)(tab, baseSize, baseLimit = h,
//                                           f, est >>>= 1, map);
//         }

//         public void forEachRemaining(Consumer<? super Map.Entry!(K, V)> action) {
//             if (action == null) throw new NullPointerException();
//             for (Node!(K, V) p; (p = advance()) != null; )
//                 action.accept(new MapEntry!(K, V)(p.key, p.val, map));
//         }

//         public boolean tryAdvance(Consumer<? super Map.Entry!(K, V)> action) {
//             if (action == null) throw new NullPointerException();
//             Node!(K, V) p;
//             if ((p = advance()) == null)
//                 return false;
//             action.accept(new MapEntry!(K, V)(p.key, p.val, map));
//             return true;
//         }

//         public long estimateSize() { return est; }

//         public int characteristics() {
//             return Spliterator.DISTINCT | Spliterator.CONCURRENT |
//                 Spliterator.NONNULL;
//         }
//     }

//     // Parallel bulk operations

//     /**
//      * Computes initial batch value for bulk tasks. The returned value
//      * is approximately exp2 of the number of times (minus one) to
//      * split task by two before executing leaf action. This value is
//      * faster to compute and more convenient to use as a guide to
//      * splitting than is the depth, since it is used while dividing by
//      * two anyway.
//      */
//     final int batchFor(long b) {
//         long n;
//         if (b == Long.MAX_VALUE || (n = sumCount()) <= 1L || n < b)
//             return 0;
//         int sp = ForkJoinPool.getCommonPoolParallelism() << 2; // slack of 4
//         return (b <= 0L || (n /= b) >= sp) ? sp : (int)n;
//     }

//     /**
//      * Performs the given action for each (key, value).
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param action the action
//      */
//     public void forEach(long parallelismThreshold,
//                         BiConsumer<? super K,? super V> action) {
//         if (action == null) throw new NullPointerException();
//         new ForEachMappingTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              action).invoke();
//     }

//     /**
//      * Performs the given action for each non-null transformation
//      * of each (key, value).
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case the action is not applied)
//      * @param action the action
//      * @param <U> the return type of the transformer
//      */
//     public <U> void forEach(long parallelismThreshold,
//                             BiFunction<? super K, ? super V, ? extends U> transformer,
//                             Consumer<? super U> action) {
//         if (transformer == null || action == null)
//             throw new NullPointerException();
//         new ForEachTransformedMappingTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              transformer, action).invoke();
//     }

//     /**
//      * Returns a non-null result from applying the given search
//      * function on each (key, value), or null if none.  Upon
//      * success, further element processing is suppressed and the
//      * results of any other parallel invocations of the search
//      * function are ignored.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param searchFunction a function returning a non-null
//      * result on success, else null
//      * @param <U> the return type of the search function
//      * @return a non-null result from applying the given search
//      * function on each (key, value), or null if none
//      */
//     public <U> U search(long parallelismThreshold,
//                         BiFunction<? super K, ? super V, ? extends U> searchFunction) {
//         if (searchFunction == null) throw new NullPointerException();
//         return new SearchMappingsTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              searchFunction, new AtomicReference<U>()).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all (key, value) pairs using the given reducer to
//      * combine values, or null if none.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case it is not combined)
//      * @param reducer a commutative associative combining function
//      * @param <U> the return type of the transformer
//      * @return the result of accumulating the given transformation
//      * of all (key, value) pairs
//      */
//     public <U> U reduce(long parallelismThreshold,
//                         BiFunction<? super K, ? super V, ? extends U> transformer,
//                         BiFunction<? super U, ? super U, ? extends U> reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceMappingsTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all (key, value) pairs using the given reducer to
//      * combine values, and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all (key, value) pairs
//      */
//     public double reduceToDouble(long parallelismThreshold,
//                                  ToDoubleBiFunction<? super K, ? super V> transformer,
//                                  double basis,
//                                  DoubleBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceMappingsToDoubleTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all (key, value) pairs using the given reducer to
//      * combine values, and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all (key, value) pairs
//      */
//     public long reduceToLong(long parallelismThreshold,
//                              ToLongBiFunction<? super K, ? super V> transformer,
//                              long basis,
//                              LongBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceMappingsToLongTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all (key, value) pairs using the given reducer to
//      * combine values, and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all (key, value) pairs
//      */
//     public int reduceToInt(long parallelismThreshold,
//                            ToIntBiFunction<? super K, ? super V> transformer,
//                            int basis,
//                            IntBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceMappingsToIntTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Performs the given action for each key.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param action the action
//      */
//     public void forEachKey(long parallelismThreshold,
//                            Consumer<? super K> action) {
//         if (action == null) throw new NullPointerException();
//         new ForEachKeyTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              action).invoke();
//     }

//     /**
//      * Performs the given action for each non-null transformation
//      * of each key.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case the action is not applied)
//      * @param action the action
//      * @param <U> the return type of the transformer
//      */
//     public <U> void forEachKey(long parallelismThreshold,
//                                Function<? super K, ? extends U> transformer,
//                                Consumer<? super U> action) {
//         if (transformer == null || action == null)
//             throw new NullPointerException();
//         new ForEachTransformedKeyTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              transformer, action).invoke();
//     }

//     /**
//      * Returns a non-null result from applying the given search
//      * function on each key, or null if none. Upon success,
//      * further element processing is suppressed and the results of
//      * any other parallel invocations of the search function are
//      * ignored.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param searchFunction a function returning a non-null
//      * result on success, else null
//      * @param <U> the return type of the search function
//      * @return a non-null result from applying the given search
//      * function on each key, or null if none
//      */
//     public <U> U searchKeys(long parallelismThreshold,
//                             Function<? super K, ? extends U> searchFunction) {
//         if (searchFunction == null) throw new NullPointerException();
//         return new SearchKeysTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              searchFunction, new AtomicReference<U>()).invoke();
//     }

//     /**
//      * Returns the result of accumulating all keys using the given
//      * reducer to combine values, or null if none.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating all keys using the given
//      * reducer to combine values, or null if none
//      */
//     public K reduceKeys(long parallelismThreshold,
//                         BiFunction<? super K, ? super K, ? extends K> reducer) {
//         if (reducer == null) throw new NullPointerException();
//         return new ReduceKeysTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all keys using the given reducer to combine values, or
//      * null if none.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case it is not combined)
//      * @param reducer a commutative associative combining function
//      * @param <U> the return type of the transformer
//      * @return the result of accumulating the given transformation
//      * of all keys
//      */
//     public <U> U reduceKeys(long parallelismThreshold,
//                             Function<? super K, ? extends U> transformer,
//          BiFunction<? super U, ? super U, ? extends U> reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceKeysTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all keys using the given reducer to combine values, and
//      * the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all keys
//      */
//     public double reduceKeysToDouble(long parallelismThreshold,
//                                      ToDoubleFunction<? super K> transformer,
//                                      double basis,
//                                      DoubleBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceKeysToDoubleTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all keys using the given reducer to combine values, and
//      * the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all keys
//      */
//     public long reduceKeysToLong(long parallelismThreshold,
//                                  ToLongFunction<? super K> transformer,
//                                  long basis,
//                                  LongBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceKeysToLongTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all keys using the given reducer to combine values, and
//      * the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all keys
//      */
//     public int reduceKeysToInt(long parallelismThreshold,
//                                ToIntFunction<? super K> transformer,
//                                int basis,
//                                IntBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceKeysToIntTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Performs the given action for each value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param action the action
//      */
//     public void forEachValue(long parallelismThreshold,
//                              Consumer<? super V> action) {
//         if (action == null)
//             throw new NullPointerException();
//         new ForEachValueTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              action).invoke();
//     }

//     /**
//      * Performs the given action for each non-null transformation
//      * of each value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case the action is not applied)
//      * @param action the action
//      * @param <U> the return type of the transformer
//      */
//     public <U> void forEachValue(long parallelismThreshold,
//                                  Function<? super V, ? extends U> transformer,
//                                  Consumer<? super U> action) {
//         if (transformer == null || action == null)
//             throw new NullPointerException();
//         new ForEachTransformedValueTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              transformer, action).invoke();
//     }

//     /**
//      * Returns a non-null result from applying the given search
//      * function on each value, or null if none.  Upon success,
//      * further element processing is suppressed and the results of
//      * any other parallel invocations of the search function are
//      * ignored.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param searchFunction a function returning a non-null
//      * result on success, else null
//      * @param <U> the return type of the search function
//      * @return a non-null result from applying the given search
//      * function on each value, or null if none
//      */
//     public <U> U searchValues(long parallelismThreshold,
//                               Function<? super V, ? extends U> searchFunction) {
//         if (searchFunction == null) throw new NullPointerException();
//         return new SearchValuesTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              searchFunction, new AtomicReference<U>()).invoke();
//     }

//     /**
//      * Returns the result of accumulating all values using the
//      * given reducer to combine values, or null if none.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating all values
//      */
//     public V reduceValues(long parallelismThreshold,
//                           BiFunction<? super V, ? super V, ? extends V> reducer) {
//         if (reducer == null) throw new NullPointerException();
//         return new ReduceValuesTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all values using the given reducer to combine values, or
//      * null if none.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case it is not combined)
//      * @param reducer a commutative associative combining function
//      * @param <U> the return type of the transformer
//      * @return the result of accumulating the given transformation
//      * of all values
//      */
//     public <U> U reduceValues(long parallelismThreshold,
//                               Function<? super V, ? extends U> transformer,
//                               BiFunction<? super U, ? super U, ? extends U> reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceValuesTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all values using the given reducer to combine values,
//      * and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all values
//      */
//     public double reduceValuesToDouble(long parallelismThreshold,
//                                        ToDoubleFunction<? super V> transformer,
//                                        double basis,
//                                        DoubleBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceValuesToDoubleTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all values using the given reducer to combine values,
//      * and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all values
//      */
//     public long reduceValuesToLong(long parallelismThreshold,
//                                    ToLongFunction<? super V> transformer,
//                                    long basis,
//                                    LongBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceValuesToLongTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all values using the given reducer to combine values,
//      * and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all values
//      */
//     public int reduceValuesToInt(long parallelismThreshold,
//                                  ToIntFunction<? super V> transformer,
//                                  int basis,
//                                  IntBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceValuesToIntTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Performs the given action for each entry.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param action the action
//      */
//     public void forEachEntry(long parallelismThreshold,
//                              Consumer<? super Map.Entry!(K, V)> action) {
//         if (action == null) throw new NullPointerException();
//         new ForEachEntryTask!(K, V)(null, batchFor(parallelismThreshold), 0, 0, table,
//                                   action).invoke();
//     }

//     /**
//      * Performs the given action for each non-null transformation
//      * of each entry.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case the action is not applied)
//      * @param action the action
//      * @param <U> the return type of the transformer
//      */
//     public <U> void forEachEntry(long parallelismThreshold,
//                                  Function<Map.Entry!(K, V), ? extends U> transformer,
//                                  Consumer<? super U> action) {
//         if (transformer == null || action == null)
//             throw new NullPointerException();
//         new ForEachTransformedEntryTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              transformer, action).invoke();
//     }

//     /**
//      * Returns a non-null result from applying the given search
//      * function on each entry, or null if none.  Upon success,
//      * further element processing is suppressed and the results of
//      * any other parallel invocations of the search function are
//      * ignored.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param searchFunction a function returning a non-null
//      * result on success, else null
//      * @param <U> the return type of the search function
//      * @return a non-null result from applying the given search
//      * function on each entry, or null if none
//      */
//     public <U> U searchEntries(long parallelismThreshold,
//                                Function<Map.Entry!(K, V), ? extends U> searchFunction) {
//         if (searchFunction == null) throw new NullPointerException();
//         return new SearchEntriesTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              searchFunction, new AtomicReference<U>()).invoke();
//     }

//     /**
//      * Returns the result of accumulating all entries using the
//      * given reducer to combine values, or null if none.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating all entries
//      */
//     public Map.Entry!(K, V) reduceEntries(long parallelismThreshold,
//                                         BiFunction<Map.Entry!(K, V), Map.Entry!(K, V), ? extends Map.Entry!(K, V)> reducer) {
//         if (reducer == null) throw new NullPointerException();
//         return new ReduceEntriesTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all entries using the given reducer to combine values,
//      * or null if none.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element, or null if there is no transformation (in
//      * which case it is not combined)
//      * @param reducer a commutative associative combining function
//      * @param <U> the return type of the transformer
//      * @return the result of accumulating the given transformation
//      * of all entries
//      */
//     public <U> U reduceEntries(long parallelismThreshold,
//                                Function<Map.Entry!(K, V), ? extends U> transformer,
//                                BiFunction<? super U, ? super U, ? extends U> reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceEntriesTask<K,V,U>
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all entries using the given reducer to combine values,
//      * and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all entries
//      */
//     public double reduceEntriesToDouble(long parallelismThreshold,
//                                         ToDoubleFunction<Map.Entry!(K, V)> transformer,
//                                         double basis,
//                                         DoubleBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceEntriesToDoubleTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all entries using the given reducer to combine values,
//      * and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all entries
//      */
//     public long reduceEntriesToLong(long parallelismThreshold,
//                                     ToLongFunction<Map.Entry!(K, V)> transformer,
//                                     long basis,
//                                     LongBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceEntriesToLongTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }

//     /**
//      * Returns the result of accumulating the given transformation
//      * of all entries using the given reducer to combine values,
//      * and the given basis as an identity value.
//      *
//      * @param parallelismThreshold the (estimated) number of elements
//      * needed for this operation to be executed in parallel
//      * @param transformer a function returning the transformation
//      * for an element
//      * @param basis the identity (initial default value) for the reduction
//      * @param reducer a commutative associative combining function
//      * @return the result of accumulating the given transformation
//      * of all entries
//      */
//     public int reduceEntriesToInt(long parallelismThreshold,
//                                   ToIntFunction<Map.Entry!(K, V)> transformer,
//                                   int basis,
//                                   IntBinaryOperator reducer) {
//         if (transformer == null || reducer == null)
//             throw new NullPointerException();
//         return new MapReduceEntriesToIntTask!(K, V)
//             (null, batchFor(parallelismThreshold), 0, 0, table,
//              null, transformer, basis, reducer).invoke();
//     }


//     /* ----------------Views -------------- */

//     /**
//      * Base class for views.
//      */
//     abstract static class CollectionView<K,V,E>
//         implements Collection<E>, java.io.Serializable {
//         private static final long serialVersionUID = 7249069246763182397L;
//         final ConcurrentHashMap!(K, V) map;
//         CollectionView(ConcurrentHashMap!(K, V) map)  { this.map = map; }

//         /**
//          * Returns the map backing this view.
//          *
//          * @return the map backing this view
//          */
//         public ConcurrentHashMap!(K, V) getMap() { return map; }

//         /**
//          * Removes all of the elements from this view, by removing all
//          * the mappings from the map backing this view.
//          */
//         public final void clear()      { map.clear(); }
//         public final int size()        { return map.size(); }
//         public final boolean isEmpty() { return map.isEmpty(); }

//         // implementations below rely on concrete classes supplying these
//         // abstract methods
//         /**
//          * Returns an iterator over the elements in this collection.
//          *
//          * <p>The returned iterator is
//          * <a href="package-summary.html#Weakly"><i>weakly consistent</i></a>.
//          *
//          * @return an iterator over the elements in this collection
//          */
//         public abstract Iterator<E> iterator();
//         public abstract boolean contains(Object o);
//         public abstract boolean remove(Object o);

//         private static final String OOME_MSG = "Required array size too large";

//         public final Object[] toArray() {
//             long sz = map.mappingCount();
//             if (sz > MAX_ARRAY_SIZE)
//                 throw new OutOfMemoryError(OOME_MSG);
//             int n = (int)sz;
//             Object[] r = new Object[n];
//             int i = 0;
//             for (E e : this) {
//                 if (i == n) {
//                     if (n >= MAX_ARRAY_SIZE)
//                         throw new OutOfMemoryError(OOME_MSG);
//                     if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
//                         n = MAX_ARRAY_SIZE;
//                     else
//                         n += (n >>> 1) + 1;
//                     r = Arrays.copyOf(r, n);
//                 }
//                 r[i++] = e;
//             }
//             return (i == n) ? r : Arrays.copyOf(r, i);
//         }

        
//         public final <T> T[] toArray(T[] a) {
//             long sz = map.mappingCount();
//             if (sz > MAX_ARRAY_SIZE)
//                 throw new OutOfMemoryError(OOME_MSG);
//             int m = (int)sz;
//             T[] r = (a.length >= m) ? a :
//                 (T[])java.lang.reflect.Array
//                 .newInstance(a.getClass().getComponentType(), m);
//             int n = r.length;
//             int i = 0;
//             for (E e : this) {
//                 if (i == n) {
//                     if (n >= MAX_ARRAY_SIZE)
//                         throw new OutOfMemoryError(OOME_MSG);
//                     if (n >= MAX_ARRAY_SIZE - (MAX_ARRAY_SIZE >>> 1) - 1)
//                         n = MAX_ARRAY_SIZE;
//                     else
//                         n += (n >>> 1) + 1;
//                     r = Arrays.copyOf(r, n);
//                 }
//                 r[i++] = (T)e;
//             }
//             if (a == r && i < n) {
//                 r[i] = null; // null-terminate
//                 return r;
//             }
//             return (i == n) ? r : Arrays.copyOf(r, i);
//         }

//         /**
//          * Returns a string representation of this collection.
//          * The string representation consists of the string representations
//          * of the collection's elements in the order they are returned by
//          * its iterator, enclosed in square brackets ({@code "[]"}).
//          * Adjacent elements are separated by the characters {@code ", "}
//          * (comma and space).  Elements are converted to strings as by
//          * {@link String#valueOf(Object)}.
//          *
//          * @return a string representation of this collection
//          */
//         public final String toString() {
//             StringBuilder sb = new StringBuilder();
//             sb.append('[');
//             Iterator<E> it = iterator();
//             if (it.hasNext()) {
//                 for (;;) {
//                     Object e = it.next();
//                     sb.append(e == this ? "(this Collection)" : e);
//                     if (!it.hasNext())
//                         break;
//                     sb.append(',').append(' ');
//                 }
//             }
//             return sb.append(']').toString();
//         }

//         public final boolean containsAll(Collection<?> c) {
//             if (c != this) {
//                 for (Object e : c) {
//                     if (e == null || !contains(e))
//                         return false;
//                 }
//             }
//             return true;
//         }

//         public boolean removeAll(Collection<?> c) {
//             if (c == null) throw new NullPointerException();
//             boolean modified = false;
//             // Use (c instanceof Set) as a hint that lookup in c is as
//             // efficient as this view
//             Node!(K, V)[] t;
//             if ((t = map.table) == null) {
//                 return false;
//             } else if (c instanceof Set<?> && c.size() > t.length) {
//                 for (Iterator<?> it = iterator(); it.hasNext(); ) {
//                     if (c.contains(it.next())) {
//                         it.remove();
//                         modified = true;
//                     }
//                 }
//             } else {
//                 for (Object e : c)
//                     modified |= remove(e);
//             }
//             return modified;
//         }

//         public final boolean retainAll(Collection<?> c) {
//             if (c == null) throw new NullPointerException();
//             boolean modified = false;
//             for (Iterator<E> it = iterator(); it.hasNext();) {
//                 if (!c.contains(it.next())) {
//                     it.remove();
//                     modified = true;
//                 }
//             }
//             return modified;
//         }

//     }

//     /**
//      * A view of a ConcurrentHashMap as a {@link Set} of keys, in
//      * which additions may optionally be enabled by mapping to a
//      * common value.  This class cannot be directly instantiated.
//      * See {@link #keySet() keySet()},
//      * {@link #keySet(Object) keySet(V)},
//      * {@link #newKeySet() newKeySet()},
//      * {@link #newKeySet(int) newKeySet(int)}.
//      *
//      */
//     public static class KeySetView!(K, V) extends CollectionView<K,V,K>
//         implements Set<K>, java.io.Serializable {
//         private static final long serialVersionUID = 7249069246763182397L;
//         private final V value;
//         KeySetView(ConcurrentHashMap!(K, V) map, V value) {  // non-public
//             super(map);
//             this.value = value;
//         }

//         /**
//          * Returns the default mapped value for additions,
//          * or {@code null} if additions are not supported.
//          *
//          * @return the default mapped value for additions, or {@code null}
//          * if not supported
//          */
//         public V getMappedValue() { return value; }

//         /**
//          * {@inheritDoc}
//          * @throws NullPointerException if the specified key is null
//          */
//         public boolean contains(Object o) { return map.containsKey(o); }

//         /**
//          * Removes the key from this map view, by removing the key (and its
//          * corresponding value) from the backing map.  This method does
//          * nothing if the key is not in the map.
//          *
//          * @param  o the key to be removed from the backing map
//          * @return {@code true} if the backing map contained the specified key
//          * @throws NullPointerException if the specified key is null
//          */
//         public boolean remove(Object o) { return map.remove(o) != null; }

//         /**
//          * @return an iterator over the keys of the backing map
//          */
//         public Iterator<K> iterator() {
//             Node!(K, V)[] t;
//             ConcurrentHashMap!(K, V) m = map;
//             int f = (t = m.table) == null ? 0 : t.length;
//             return new KeyIterator!(K, V)(t, f, 0, f, m);
//         }

//         /**
//          * Adds the specified key to this set view by mapping the key to
//          * the default mapped value in the backing map, if defined.
//          *
//          * @param e key to be added
//          * @return {@code true} if this set changed as a result of the call
//          * @throws NullPointerException if the specified key is null
//          * @throws UnsupportedOperationException if no default mapped value
//          * for additions was provided
//          */
//         public boolean add(K e) {
//             V v;
//             if ((v = value) == null)
//                 throw new UnsupportedOperationException();
//             return map.putVal(e, v, true) == null;
//         }

//         /**
//          * Adds all of the elements in the specified collection to this set,
//          * as if by calling {@link #add} on each one.
//          *
//          * @param c the elements to be inserted into this set
//          * @return {@code true} if this set changed as a result of the call
//          * @throws NullPointerException if the collection or any of its
//          * elements are {@code null}
//          * @throws UnsupportedOperationException if no default mapped value
//          * for additions was provided
//          */
//         public boolean addAll(Collection<? extends K> c) {
//             boolean added = false;
//             V v;
//             if ((v = value) == null)
//                 throw new UnsupportedOperationException();
//             for (K e : c) {
//                 if (map.putVal(e, v, true) == null)
//                     added = true;
//             }
//             return added;
//         }

//         public int hashCode() {
//             int h = 0;
//             for (K e : this)
//                 h += e.hashCode();
//             return h;
//         }

//         public boolean equals(Object o) {
//             Set<?> c;
//             return ((o instanceof Set) &&
//                     ((c = (Set<?>)o) == this ||
//                      (containsAll(c) && c.containsAll(this))));
//         }

//         public Spliterator<K> spliterator() {
//             Node!(K, V)[] t;
//             ConcurrentHashMap!(K, V) m = map;
//             long n = m.sumCount();
//             int f = (t = m.table) == null ? 0 : t.length;
//             return new KeySpliterator!(K, V)(t, f, 0, f, n < 0L ? 0L : n);
//         }

//         public void forEach(Consumer<? super K> action) {
//             if (action == null) throw new NullPointerException();
//             Node!(K, V)[] t;
//             if ((t = map.table) != null) {
//                 Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//                 for (Node!(K, V) p; (p = it.advance()) != null; )
//                     action.accept(p.key);
//             }
//         }
//     }

//     /**
//      * A view of a ConcurrentHashMap as a {@link Collection} of
//      * values, in which additions are disabled. This class cannot be
//      * directly instantiated. See {@link #values()}.
//      */
//     static final class ValuesView!(K, V) extends CollectionView<K,V,V>
//         implements Collection<V>, java.io.Serializable {
//         private static final long serialVersionUID = 2249069246763182397L;
//         ValuesView(ConcurrentHashMap!(K, V) map) { super(map); }
//         public final boolean contains(Object o) {
//             return map.containsValue(o);
//         }

//         public final boolean remove(Object o) {
//             if (o != null) {
//                 for (Iterator<V> it = iterator(); it.hasNext();) {
//                     if (o.equals(it.next())) {
//                         it.remove();
//                         return true;
//                     }
//                 }
//             }
//             return false;
//         }

//         public final Iterator<V> iterator() {
//             ConcurrentHashMap!(K, V) m = map;
//             Node!(K, V)[] t;
//             int f = (t = m.table) == null ? 0 : t.length;
//             return new ValueIterator!(K, V)(t, f, 0, f, m);
//         }

//         public final boolean add(V e) {
//             throw new UnsupportedOperationException();
//         }
//         public final boolean addAll(Collection<? extends V> c) {
//             throw new UnsupportedOperationException();
//         }

//         @Override public boolean removeAll(Collection<?> c) {
//             if (c == null) throw new NullPointerException();
//             boolean modified = false;
//             for (Iterator<V> it = iterator(); it.hasNext();) {
//                 if (c.contains(it.next())) {
//                     it.remove();
//                     modified = true;
//                 }
//             }
//             return modified;
//         }

//         public boolean removeIf(Predicate<? super V> filter) {
//             return map.removeValueIf(filter);
//         }

//         public Spliterator<V> spliterator() {
//             Node!(K, V)[] t;
//             ConcurrentHashMap!(K, V) m = map;
//             long n = m.sumCount();
//             int f = (t = m.table) == null ? 0 : t.length;
//             return new ValueSpliterator!(K, V)(t, f, 0, f, n < 0L ? 0L : n);
//         }

//         public void forEach(Consumer<? super V> action) {
//             if (action == null) throw new NullPointerException();
//             Node!(K, V)[] t;
//             if ((t = map.table) != null) {
//                 Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//                 for (Node!(K, V) p; (p = it.advance()) != null; )
//                     action.accept(p.val);
//             }
//         }
//     }

//     /**
//      * A view of a ConcurrentHashMap as a {@link Set} of (key, value)
//      * entries.  This class cannot be directly instantiated. See
//      * {@link #entrySet()}.
//      */
//     static final class EntrySetView!(K, V) extends CollectionView<K,V,Map.Entry!(K, V)>
//         implements Set<Map.Entry!(K, V)>, java.io.Serializable {
//         private static final long serialVersionUID = 2249069246763182397L;
//         EntrySetView(ConcurrentHashMap!(K, V) map) { super(map); }

//         public boolean contains(Object o) {
//             Object k, v, r; Map.Entry<?,?> e;
//             return ((o instanceof Map.Entry) &&
//                     (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
//                     (r = map.get(k)) != null &&
//                     (v = e.getValue()) != null &&
//                     (v == r || v.equals(r)));
//         }

//         public boolean remove(Object o) {
//             Object k, v; Map.Entry<?,?> e;
//             return ((o instanceof Map.Entry) &&
//                     (k = (e = (Map.Entry<?,?>)o).getKey()) != null &&
//                     (v = e.getValue()) != null &&
//                     map.remove(k, v));
//         }

//         /**
//          * @return an iterator over the entries of the backing map
//          */
//         public Iterator<Map.Entry!(K, V)> iterator() {
//             ConcurrentHashMap!(K, V) m = map;
//             Node!(K, V)[] t;
//             int f = (t = m.table) == null ? 0 : t.length;
//             return new EntryIterator!(K, V)(t, f, 0, f, m);
//         }

//         public boolean add(Entry!(K, V) e) {
//             return map.putVal(e.getKey(), e.getValue(), false) == null;
//         }

//         public boolean addAll(Collection<? extends Entry!(K, V)> c) {
//             boolean added = false;
//             for (Entry!(K, V) e : c) {
//                 if (add(e))
//                     added = true;
//             }
//             return added;
//         }

//         public boolean removeIf(Predicate<? super Entry!(K, V)> filter) {
//             return map.removeEntryIf(filter);
//         }

//         public final int hashCode() {
//             int h = 0;
//             Node!(K, V)[] t;
//             if ((t = map.table) != null) {
//                 Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//                 for (Node!(K, V) p; (p = it.advance()) != null; ) {
//                     h += p.hashCode();
//                 }
//             }
//             return h;
//         }

//         public final boolean equals(Object o) {
//             Set<?> c;
//             return ((o instanceof Set) &&
//                     ((c = (Set<?>)o) == this ||
//                      (containsAll(c) && c.containsAll(this))));
//         }

//         public Spliterator<Map.Entry!(K, V)> spliterator() {
//             Node!(K, V)[] t;
//             ConcurrentHashMap!(K, V) m = map;
//             long n = m.sumCount();
//             int f = (t = m.table) == null ? 0 : t.length;
//             return new EntrySpliterator!(K, V)(t, f, 0, f, n < 0L ? 0L : n, m);
//         }

//         public void forEach(Consumer<? super Map.Entry!(K, V)> action) {
//             if (action == null) throw new NullPointerException();
//             Node!(K, V)[] t;
//             if ((t = map.table) != null) {
//                 Traverser!(K, V) it = new Traverser!(K, V)(t, t.length, 0, t.length);
//                 for (Node!(K, V) p; (p = it.advance()) != null; )
//                     action.accept(new MapEntry!(K, V)(p.key, p.val, map));
//             }
//         }

//     }

//     // -------------------------------------------------------

//     /**
//      * Base class for bulk tasks. Repeats some fields and code from
//      * class Traverser, because we need to subclass CountedCompleter.
//      */
//     @SuppressWarnings("serial")
//     abstract static class BulkTask<K,V,R> extends CountedCompleter<R> {
//         Node!(K, V)[] tab;        // same as Traverser
//         Node!(K, V) next;
//         TableStack!(K, V) stack, spare;
//         int index;
//         int baseIndex;
//         int baseLimit;
//         final int baseSize;
//         int batch;              // split control

//         BulkTask(BulkTask<K,V,?> par, int b, int i, int f, Node!(K, V)[] t) {
//             super(par);
//             this.batch = b;
//             this.index = this.baseIndex = i;
//             if ((this.tab = t) == null)
//                 this.baseSize = this.baseLimit = 0;
//             else if (par == null)
//                 this.baseSize = this.baseLimit = t.length;
//             else {
//                 this.baseLimit = f;
//                 this.baseSize = par.baseSize;
//             }
//         }

//         /**
//          * Same as Traverser version.
//          */
//         final Node!(K, V) advance() {
//             Node!(K, V) e;
//             if ((e = next) != null)
//                 e = e.next;
//             for (;;) {
//                 Node!(K, V)[] t; int i, n;
//                 if (e != null)
//                     return next = e;
//                 if (baseIndex >= baseLimit || (t = tab) == null ||
//                     (n = t.length) <= (i = index) || i < 0)
//                     return next = null;
//                 if ((e = tabAt(t, i)) != null && e.hash < 0) {
//                     if (e instanceof ForwardingNode) {
//                         tab = ((ForwardingNode!(K, V))e).nextTable;
//                         e = null;
//                         pushState(t, i, n);
//                         continue;
//                     }
//                     else if (e instanceof TreeBin)
//                         e = ((TreeBin!(K, V))e).first;
//                     else
//                         e = null;
//                 }
//                 if (stack != null)
//                     recoverState(n);
//                 else if ((index = i + baseSize) >= n)
//                     index = ++baseIndex;
//             }
//         }

//         private void pushState(Node!(K, V)[] t, int i, int n) {
//             TableStack!(K, V) s = spare;
//             if (s != null)
//                 spare = s.next;
//             else
//                 s = new TableStack!(K, V)();
//             s.tab = t;
//             s.length = n;
//             s.index = i;
//             s.next = stack;
//             stack = s;
//         }

//         private void recoverState(int n) {
//             TableStack!(K, V) s; int len;
//             while ((s = stack) != null && (index += (len = s.length)) >= n) {
//                 n = len;
//                 index = s.index;
//                 tab = s.tab;
//                 s.tab = null;
//                 TableStack!(K, V) next = s.next;
//                 s.next = spare; // save for reuse
//                 stack = next;
//                 spare = s;
//             }
//             if (s == null && (index += baseSize) >= n)
//                 index = ++baseIndex;
//         }
//     }

//     /*
//      * Task classes. Coded in a regular but ugly format/style to
//      * simplify checks that each variant differs in the right way from
//      * others. The null screenings exist because compilers cannot tell
//      * that we've already null-checked task arguments, so we force
//      * simplest hoisted bypass to help avoid convoluted traps.
//      */
//     @SuppressWarnings("serial")
//     static final class ForEachKeyTask!(K, V)
//         extends BulkTask<K,V,Void> {
//         final Consumer<? super K> action;
//         ForEachKeyTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Consumer<? super K> action) {
//             super(p, b, i, f, t);
//             this.action = action;
//         }
//         public final void compute() {
//             final Consumer<? super K> action;
//             if ((action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachKeyTask!(K, V)
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null;)
//                     action.accept(p.key);
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ForEachValueTask!(K, V)
//         extends BulkTask<K,V,Void> {
//         final Consumer<? super V> action;
//         ForEachValueTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Consumer<? super V> action) {
//             super(p, b, i, f, t);
//             this.action = action;
//         }
//         public final void compute() {
//             final Consumer<? super V> action;
//             if ((action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachValueTask!(K, V)
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null;)
//                     action.accept(p.val);
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ForEachEntryTask!(K, V)
//         extends BulkTask<K,V,Void> {
//         final Consumer<? super Entry!(K, V)> action;
//         ForEachEntryTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Consumer<? super Entry!(K, V)> action) {
//             super(p, b, i, f, t);
//             this.action = action;
//         }
//         public final void compute() {
//             final Consumer<? super Entry!(K, V)> action;
//             if ((action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachEntryTask!(K, V)
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     action.accept(p);
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ForEachMappingTask!(K, V)
//         extends BulkTask<K,V,Void> {
//         final BiConsumer<? super K, ? super V> action;
//         ForEachMappingTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              BiConsumer<? super K,? super V> action) {
//             super(p, b, i, f, t);
//             this.action = action;
//         }
//         public final void compute() {
//             final BiConsumer<? super K, ? super V> action;
//             if ((action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachMappingTask!(K, V)
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     action.accept(p.key, p.val);
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ForEachTransformedKeyTask<K,V,U>
//         extends BulkTask<K,V,Void> {
//         final Function<? super K, ? extends U> transformer;
//         final Consumer<? super U> action;
//         ForEachTransformedKeyTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Function<? super K, ? extends U> transformer, Consumer<? super U> action) {
//             super(p, b, i, f, t);
//             this.transformer = transformer; this.action = action;
//         }
//         public final void compute() {
//             final Function<? super K, ? extends U> transformer;
//             final Consumer<? super U> action;
//             if ((transformer = this.transformer) != null &&
//                 (action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachTransformedKeyTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          transformer, action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p.key)) != null)
//                         action.accept(u);
//                 }
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ForEachTransformedValueTask<K,V,U>
//         extends BulkTask<K,V,Void> {
//         final Function<? super V, ? extends U> transformer;
//         final Consumer<? super U> action;
//         ForEachTransformedValueTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Function<? super V, ? extends U> transformer, Consumer<? super U> action) {
//             super(p, b, i, f, t);
//             this.transformer = transformer; this.action = action;
//         }
//         public final void compute() {
//             final Function<? super V, ? extends U> transformer;
//             final Consumer<? super U> action;
//             if ((transformer = this.transformer) != null &&
//                 (action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachTransformedValueTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          transformer, action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p.val)) != null)
//                         action.accept(u);
//                 }
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ForEachTransformedEntryTask<K,V,U>
//         extends BulkTask<K,V,Void> {
//         final Function<Map.Entry!(K, V), ? extends U> transformer;
//         final Consumer<? super U> action;
//         ForEachTransformedEntryTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Function<Map.Entry!(K, V), ? extends U> transformer, Consumer<? super U> action) {
//             super(p, b, i, f, t);
//             this.transformer = transformer; this.action = action;
//         }
//         public final void compute() {
//             final Function<Map.Entry!(K, V), ? extends U> transformer;
//             final Consumer<? super U> action;
//             if ((transformer = this.transformer) != null &&
//                 (action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachTransformedEntryTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          transformer, action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p)) != null)
//                         action.accept(u);
//                 }
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ForEachTransformedMappingTask<K,V,U>
//         extends BulkTask<K,V,Void> {
//         final BiFunction<? super K, ? super V, ? extends U> transformer;
//         final Consumer<? super U> action;
//         ForEachTransformedMappingTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              BiFunction<? super K, ? super V, ? extends U> transformer,
//              Consumer<? super U> action) {
//             super(p, b, i, f, t);
//             this.transformer = transformer; this.action = action;
//         }
//         public final void compute() {
//             final BiFunction<? super K, ? super V, ? extends U> transformer;
//             final Consumer<? super U> action;
//             if ((transformer = this.transformer) != null &&
//                 (action = this.action) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     new ForEachTransformedMappingTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          transformer, action).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p.key, p.val)) != null)
//                         action.accept(u);
//                 }
//                 propagateCompletion();
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class SearchKeysTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final Function<? super K, ? extends U> searchFunction;
//         final AtomicReference<U> result;
//         SearchKeysTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Function<? super K, ? extends U> searchFunction,
//              AtomicReference<U> result) {
//             super(p, b, i, f, t);
//             this.searchFunction = searchFunction; this.result = result;
//         }
//         public final U getRawResult() { return result.get(); }
//         public final void compute() {
//             final Function<? super K, ? extends U> searchFunction;
//             final AtomicReference<U> result;
//             if ((searchFunction = this.searchFunction) != null &&
//                 (result = this.result) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     if (result.get() != null)
//                         return;
//                     addToPendingCount(1);
//                     new SearchKeysTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          searchFunction, result).fork();
//                 }
//                 while (result.get() == null) {
//                     U u;
//                     Node!(K, V) p;
//                     if ((p = advance()) == null) {
//                         propagateCompletion();
//                         break;
//                     }
//                     if ((u = searchFunction.apply(p.key)) != null) {
//                         if (result.compareAndSet(null, u))
//                             quietlyCompleteRoot();
//                         break;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class SearchValuesTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final Function<? super V, ? extends U> searchFunction;
//         final AtomicReference<U> result;
//         SearchValuesTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Function<? super V, ? extends U> searchFunction,
//              AtomicReference<U> result) {
//             super(p, b, i, f, t);
//             this.searchFunction = searchFunction; this.result = result;
//         }
//         public final U getRawResult() { return result.get(); }
//         public final void compute() {
//             final Function<? super V, ? extends U> searchFunction;
//             final AtomicReference<U> result;
//             if ((searchFunction = this.searchFunction) != null &&
//                 (result = this.result) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     if (result.get() != null)
//                         return;
//                     addToPendingCount(1);
//                     new SearchValuesTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          searchFunction, result).fork();
//                 }
//                 while (result.get() == null) {
//                     U u;
//                     Node!(K, V) p;
//                     if ((p = advance()) == null) {
//                         propagateCompletion();
//                         break;
//                     }
//                     if ((u = searchFunction.apply(p.val)) != null) {
//                         if (result.compareAndSet(null, u))
//                             quietlyCompleteRoot();
//                         break;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class SearchEntriesTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final Function<Entry!(K, V), ? extends U> searchFunction;
//         final AtomicReference<U> result;
//         SearchEntriesTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              Function<Entry!(K, V), ? extends U> searchFunction,
//              AtomicReference<U> result) {
//             super(p, b, i, f, t);
//             this.searchFunction = searchFunction; this.result = result;
//         }
//         public final U getRawResult() { return result.get(); }
//         public final void compute() {
//             final Function<Entry!(K, V), ? extends U> searchFunction;
//             final AtomicReference<U> result;
//             if ((searchFunction = this.searchFunction) != null &&
//                 (result = this.result) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     if (result.get() != null)
//                         return;
//                     addToPendingCount(1);
//                     new SearchEntriesTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          searchFunction, result).fork();
//                 }
//                 while (result.get() == null) {
//                     U u;
//                     Node!(K, V) p;
//                     if ((p = advance()) == null) {
//                         propagateCompletion();
//                         break;
//                     }
//                     if ((u = searchFunction.apply(p)) != null) {
//                         if (result.compareAndSet(null, u))
//                             quietlyCompleteRoot();
//                         return;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class SearchMappingsTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final BiFunction<? super K, ? super V, ? extends U> searchFunction;
//         final AtomicReference<U> result;
//         SearchMappingsTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              BiFunction<? super K, ? super V, ? extends U> searchFunction,
//              AtomicReference<U> result) {
//             super(p, b, i, f, t);
//             this.searchFunction = searchFunction; this.result = result;
//         }
//         public final U getRawResult() { return result.get(); }
//         public final void compute() {
//             final BiFunction<? super K, ? super V, ? extends U> searchFunction;
//             final AtomicReference<U> result;
//             if ((searchFunction = this.searchFunction) != null &&
//                 (result = this.result) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     if (result.get() != null)
//                         return;
//                     addToPendingCount(1);
//                     new SearchMappingsTask<K,V,U>
//                         (this, batch >>>= 1, baseLimit = h, f, tab,
//                          searchFunction, result).fork();
//                 }
//                 while (result.get() == null) {
//                     U u;
//                     Node!(K, V) p;
//                     if ((p = advance()) == null) {
//                         propagateCompletion();
//                         break;
//                     }
//                     if ((u = searchFunction.apply(p.key, p.val)) != null) {
//                         if (result.compareAndSet(null, u))
//                             quietlyCompleteRoot();
//                         break;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ReduceKeysTask!(K, V)
//         extends BulkTask<K,V,K> {
//         final BiFunction<? super K, ? super K, ? extends K> reducer;
//         K result;
//         ReduceKeysTask!(K, V) rights, nextRight;
//         ReduceKeysTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              ReduceKeysTask!(K, V) nextRight,
//              BiFunction<? super K, ? super K, ? extends K> reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.reducer = reducer;
//         }
//         public final K getRawResult() { return result; }
//         public final void compute() {
//             final BiFunction<? super K, ? super K, ? extends K> reducer;
//             if ((reducer = this.reducer) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new ReduceKeysTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, reducer)).fork();
//                 }
//                 K r = null;
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     K u = p.key;
//                     r = (r == null) ? u : u == null ? r : reducer.apply(r, u);
//                 }
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     ReduceKeysTask!(K, V)
//                         t = (ReduceKeysTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         K tr, sr;
//                         if ((sr = s.result) != null)
//                             t.result = (((tr = t.result) == null) ? sr :
//                                         reducer.apply(tr, sr));
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ReduceValuesTask!(K, V)
//         extends BulkTask<K,V,V> {
//         final BiFunction<? super V, ? super V, ? extends V> reducer;
//         V result;
//         ReduceValuesTask!(K, V) rights, nextRight;
//         ReduceValuesTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              ReduceValuesTask!(K, V) nextRight,
//              BiFunction<? super V, ? super V, ? extends V> reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.reducer = reducer;
//         }
//         public final V getRawResult() { return result; }
//         public final void compute() {
//             final BiFunction<? super V, ? super V, ? extends V> reducer;
//             if ((reducer = this.reducer) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new ReduceValuesTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, reducer)).fork();
//                 }
//                 V r = null;
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     V v = p.val;
//                     r = (r == null) ? v : reducer.apply(r, v);
//                 }
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     ReduceValuesTask!(K, V)
//                         t = (ReduceValuesTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         V tr, sr;
//                         if ((sr = s.result) != null)
//                             t.result = (((tr = t.result) == null) ? sr :
//                                         reducer.apply(tr, sr));
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class ReduceEntriesTask!(K, V)
//         extends BulkTask<K,V,Map.Entry!(K, V)> {
//         final BiFunction<Map.Entry!(K, V), Map.Entry!(K, V), ? extends Map.Entry!(K, V)> reducer;
//         Map.Entry!(K, V) result;
//         ReduceEntriesTask!(K, V) rights, nextRight;
//         ReduceEntriesTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              ReduceEntriesTask!(K, V) nextRight,
//              BiFunction<Entry!(K, V), Map.Entry!(K, V), ? extends Map.Entry!(K, V)> reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.reducer = reducer;
//         }
//         public final Map.Entry!(K, V) getRawResult() { return result; }
//         public final void compute() {
//             final BiFunction<Map.Entry!(K, V), Map.Entry!(K, V), ? extends Map.Entry!(K, V)> reducer;
//             if ((reducer = this.reducer) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new ReduceEntriesTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, reducer)).fork();
//                 }
//                 Map.Entry!(K, V) r = null;
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = (r == null) ? p : reducer.apply(r, p);
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     ReduceEntriesTask!(K, V)
//                         t = (ReduceEntriesTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         Map.Entry!(K, V) tr, sr;
//                         if ((sr = s.result) != null)
//                             t.result = (((tr = t.result) == null) ? sr :
//                                         reducer.apply(tr, sr));
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceKeysTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final Function<? super K, ? extends U> transformer;
//         final BiFunction<? super U, ? super U, ? extends U> reducer;
//         U result;
//         MapReduceKeysTask<K,V,U> rights, nextRight;
//         MapReduceKeysTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceKeysTask<K,V,U> nextRight,
//              Function<? super K, ? extends U> transformer,
//              BiFunction<? super U, ? super U, ? extends U> reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.reducer = reducer;
//         }
//         public final U getRawResult() { return result; }
//         public final void compute() {
//             final Function<? super K, ? extends U> transformer;
//             final BiFunction<? super U, ? super U, ? extends U> reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceKeysTask<K,V,U>
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, reducer)).fork();
//                 }
//                 U r = null;
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p.key)) != null)
//                         r = (r == null) ? u : reducer.apply(r, u);
//                 }
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceKeysTask<K,V,U>
//                         t = (MapReduceKeysTask<K,V,U>)c,
//                         s = t.rights;
//                     while (s != null) {
//                         U tr, sr;
//                         if ((sr = s.result) != null)
//                             t.result = (((tr = t.result) == null) ? sr :
//                                         reducer.apply(tr, sr));
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceValuesTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final Function<? super V, ? extends U> transformer;
//         final BiFunction<? super U, ? super U, ? extends U> reducer;
//         U result;
//         MapReduceValuesTask<K,V,U> rights, nextRight;
//         MapReduceValuesTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceValuesTask<K,V,U> nextRight,
//              Function<? super V, ? extends U> transformer,
//              BiFunction<? super U, ? super U, ? extends U> reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.reducer = reducer;
//         }
//         public final U getRawResult() { return result; }
//         public final void compute() {
//             final Function<? super V, ? extends U> transformer;
//             final BiFunction<? super U, ? super U, ? extends U> reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceValuesTask<K,V,U>
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, reducer)).fork();
//                 }
//                 U r = null;
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p.val)) != null)
//                         r = (r == null) ? u : reducer.apply(r, u);
//                 }
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceValuesTask<K,V,U>
//                         t = (MapReduceValuesTask<K,V,U>)c,
//                         s = t.rights;
//                     while (s != null) {
//                         U tr, sr;
//                         if ((sr = s.result) != null)
//                             t.result = (((tr = t.result) == null) ? sr :
//                                         reducer.apply(tr, sr));
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceEntriesTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final Function<Map.Entry!(K, V), ? extends U> transformer;
//         final BiFunction<? super U, ? super U, ? extends U> reducer;
//         U result;
//         MapReduceEntriesTask<K,V,U> rights, nextRight;
//         MapReduceEntriesTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceEntriesTask<K,V,U> nextRight,
//              Function<Map.Entry!(K, V), ? extends U> transformer,
//              BiFunction<? super U, ? super U, ? extends U> reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.reducer = reducer;
//         }
//         public final U getRawResult() { return result; }
//         public final void compute() {
//             final Function<Map.Entry!(K, V), ? extends U> transformer;
//             final BiFunction<? super U, ? super U, ? extends U> reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceEntriesTask<K,V,U>
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, reducer)).fork();
//                 }
//                 U r = null;
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p)) != null)
//                         r = (r == null) ? u : reducer.apply(r, u);
//                 }
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceEntriesTask<K,V,U>
//                         t = (MapReduceEntriesTask<K,V,U>)c,
//                         s = t.rights;
//                     while (s != null) {
//                         U tr, sr;
//                         if ((sr = s.result) != null)
//                             t.result = (((tr = t.result) == null) ? sr :
//                                         reducer.apply(tr, sr));
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceMappingsTask<K,V,U>
//         extends BulkTask<K,V,U> {
//         final BiFunction<? super K, ? super V, ? extends U> transformer;
//         final BiFunction<? super U, ? super U, ? extends U> reducer;
//         U result;
//         MapReduceMappingsTask<K,V,U> rights, nextRight;
//         MapReduceMappingsTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceMappingsTask<K,V,U> nextRight,
//              BiFunction<? super K, ? super V, ? extends U> transformer,
//              BiFunction<? super U, ? super U, ? extends U> reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.reducer = reducer;
//         }
//         public final U getRawResult() { return result; }
//         public final void compute() {
//             final BiFunction<? super K, ? super V, ? extends U> transformer;
//             final BiFunction<? super U, ? super U, ? extends U> reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceMappingsTask<K,V,U>
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, reducer)).fork();
//                 }
//                 U r = null;
//                 for (Node!(K, V) p; (p = advance()) != null; ) {
//                     U u;
//                     if ((u = transformer.apply(p.key, p.val)) != null)
//                         r = (r == null) ? u : reducer.apply(r, u);
//                 }
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceMappingsTask<K,V,U>
//                         t = (MapReduceMappingsTask<K,V,U>)c,
//                         s = t.rights;
//                     while (s != null) {
//                         U tr, sr;
//                         if ((sr = s.result) != null)
//                             t.result = (((tr = t.result) == null) ? sr :
//                                         reducer.apply(tr, sr));
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceKeysToDoubleTask!(K, V)
//         extends BulkTask<K,V,Double> {
//         final ToDoubleFunction<? super K> transformer;
//         final DoubleBinaryOperator reducer;
//         final double basis;
//         double result;
//         MapReduceKeysToDoubleTask!(K, V) rights, nextRight;
//         MapReduceKeysToDoubleTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceKeysToDoubleTask!(K, V) nextRight,
//              ToDoubleFunction<? super K> transformer,
//              double basis,
//              DoubleBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Double getRawResult() { return result; }
//         public final void compute() {
//             final ToDoubleFunction<? super K> transformer;
//             final DoubleBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 double r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceKeysToDoubleTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsDouble(r, transformer.applyAsDouble(p.key));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceKeysToDoubleTask!(K, V)
//                         t = (MapReduceKeysToDoubleTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsDouble(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceValuesToDoubleTask!(K, V)
//         extends BulkTask<K,V,Double> {
//         final ToDoubleFunction<? super V> transformer;
//         final DoubleBinaryOperator reducer;
//         final double basis;
//         double result;
//         MapReduceValuesToDoubleTask!(K, V) rights, nextRight;
//         MapReduceValuesToDoubleTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceValuesToDoubleTask!(K, V) nextRight,
//              ToDoubleFunction<? super V> transformer,
//              double basis,
//              DoubleBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Double getRawResult() { return result; }
//         public final void compute() {
//             final ToDoubleFunction<? super V> transformer;
//             final DoubleBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 double r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceValuesToDoubleTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsDouble(r, transformer.applyAsDouble(p.val));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceValuesToDoubleTask!(K, V)
//                         t = (MapReduceValuesToDoubleTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsDouble(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceEntriesToDoubleTask!(K, V)
//         extends BulkTask<K,V,Double> {
//         final ToDoubleFunction<Map.Entry!(K, V)> transformer;
//         final DoubleBinaryOperator reducer;
//         final double basis;
//         double result;
//         MapReduceEntriesToDoubleTask!(K, V) rights, nextRight;
//         MapReduceEntriesToDoubleTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceEntriesToDoubleTask!(K, V) nextRight,
//              ToDoubleFunction<Map.Entry!(K, V)> transformer,
//              double basis,
//              DoubleBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Double getRawResult() { return result; }
//         public final void compute() {
//             final ToDoubleFunction<Map.Entry!(K, V)> transformer;
//             final DoubleBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 double r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceEntriesToDoubleTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsDouble(r, transformer.applyAsDouble(p));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceEntriesToDoubleTask!(K, V)
//                         t = (MapReduceEntriesToDoubleTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsDouble(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceMappingsToDoubleTask!(K, V)
//         extends BulkTask<K,V,Double> {
//         final ToDoubleBiFunction<? super K, ? super V> transformer;
//         final DoubleBinaryOperator reducer;
//         final double basis;
//         double result;
//         MapReduceMappingsToDoubleTask!(K, V) rights, nextRight;
//         MapReduceMappingsToDoubleTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceMappingsToDoubleTask!(K, V) nextRight,
//              ToDoubleBiFunction<? super K, ? super V> transformer,
//              double basis,
//              DoubleBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Double getRawResult() { return result; }
//         public final void compute() {
//             final ToDoubleBiFunction<? super K, ? super V> transformer;
//             final DoubleBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 double r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceMappingsToDoubleTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsDouble(r, transformer.applyAsDouble(p.key, p.val));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceMappingsToDoubleTask!(K, V)
//                         t = (MapReduceMappingsToDoubleTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsDouble(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceKeysToLongTask!(K, V)
//         extends BulkTask<K,V,Long> {
//         final ToLongFunction<? super K> transformer;
//         final LongBinaryOperator reducer;
//         final long basis;
//         long result;
//         MapReduceKeysToLongTask!(K, V) rights, nextRight;
//         MapReduceKeysToLongTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceKeysToLongTask!(K, V) nextRight,
//              ToLongFunction<? super K> transformer,
//              long basis,
//              LongBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Long getRawResult() { return result; }
//         public final void compute() {
//             final ToLongFunction<? super K> transformer;
//             final LongBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 long r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceKeysToLongTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsLong(r, transformer.applyAsLong(p.key));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceKeysToLongTask!(K, V)
//                         t = (MapReduceKeysToLongTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsLong(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceValuesToLongTask!(K, V)
//         extends BulkTask<K,V,Long> {
//         final ToLongFunction<? super V> transformer;
//         final LongBinaryOperator reducer;
//         final long basis;
//         long result;
//         MapReduceValuesToLongTask!(K, V) rights, nextRight;
//         MapReduceValuesToLongTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceValuesToLongTask!(K, V) nextRight,
//              ToLongFunction<? super V> transformer,
//              long basis,
//              LongBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Long getRawResult() { return result; }
//         public final void compute() {
//             final ToLongFunction<? super V> transformer;
//             final LongBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 long r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceValuesToLongTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsLong(r, transformer.applyAsLong(p.val));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceValuesToLongTask!(K, V)
//                         t = (MapReduceValuesToLongTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsLong(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceEntriesToLongTask!(K, V)
//         extends BulkTask<K,V,Long> {
//         final ToLongFunction<Map.Entry!(K, V)> transformer;
//         final LongBinaryOperator reducer;
//         final long basis;
//         long result;
//         MapReduceEntriesToLongTask!(K, V) rights, nextRight;
//         MapReduceEntriesToLongTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceEntriesToLongTask!(K, V) nextRight,
//              ToLongFunction<Map.Entry!(K, V)> transformer,
//              long basis,
//              LongBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Long getRawResult() { return result; }
//         public final void compute() {
//             final ToLongFunction<Map.Entry!(K, V)> transformer;
//             final LongBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 long r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceEntriesToLongTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsLong(r, transformer.applyAsLong(p));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceEntriesToLongTask!(K, V)
//                         t = (MapReduceEntriesToLongTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsLong(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceMappingsToLongTask!(K, V)
//         extends BulkTask<K,V,Long> {
//         final ToLongBiFunction<? super K, ? super V> transformer;
//         final LongBinaryOperator reducer;
//         final long basis;
//         long result;
//         MapReduceMappingsToLongTask!(K, V) rights, nextRight;
//         MapReduceMappingsToLongTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceMappingsToLongTask!(K, V) nextRight,
//              ToLongBiFunction<? super K, ? super V> transformer,
//              long basis,
//              LongBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Long getRawResult() { return result; }
//         public final void compute() {
//             final ToLongBiFunction<? super K, ? super V> transformer;
//             final LongBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 long r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceMappingsToLongTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsLong(r, transformer.applyAsLong(p.key, p.val));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceMappingsToLongTask!(K, V)
//                         t = (MapReduceMappingsToLongTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsLong(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceKeysToIntTask!(K, V)
//         extends BulkTask<K,V,Integer> {
//         final ToIntFunction<? super K> transformer;
//         final IntBinaryOperator reducer;
//         final int basis;
//         int result;
//         MapReduceKeysToIntTask!(K, V) rights, nextRight;
//         MapReduceKeysToIntTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceKeysToIntTask!(K, V) nextRight,
//              ToIntFunction<? super K> transformer,
//              int basis,
//              IntBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Integer getRawResult() { return result; }
//         public final void compute() {
//             final ToIntFunction<? super K> transformer;
//             final IntBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 int r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceKeysToIntTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsInt(r, transformer.applyAsInt(p.key));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceKeysToIntTask!(K, V)
//                         t = (MapReduceKeysToIntTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsInt(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceValuesToIntTask!(K, V)
//         extends BulkTask<K,V,Integer> {
//         final ToIntFunction<? super V> transformer;
//         final IntBinaryOperator reducer;
//         final int basis;
//         int result;
//         MapReduceValuesToIntTask!(K, V) rights, nextRight;
//         MapReduceValuesToIntTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceValuesToIntTask!(K, V) nextRight,
//              ToIntFunction<? super V> transformer,
//              int basis,
//              IntBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Integer getRawResult() { return result; }
//         public final void compute() {
//             final ToIntFunction<? super V> transformer;
//             final IntBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 int r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceValuesToIntTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsInt(r, transformer.applyAsInt(p.val));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceValuesToIntTask!(K, V)
//                         t = (MapReduceValuesToIntTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsInt(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     @SuppressWarnings("serial")
//     static final class MapReduceEntriesToIntTask!(K, V)
//         extends BulkTask<K,V,Integer> {
//         final ToIntFunction<Map.Entry!(K, V)> transformer;
//         final IntBinaryOperator reducer;
//         final int basis;
//         int result;
//         MapReduceEntriesToIntTask!(K, V) rights, nextRight;
//         MapReduceEntriesToIntTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceEntriesToIntTask!(K, V) nextRight,
//              ToIntFunction<Map.Entry!(K, V)> transformer,
//              int basis,
//              IntBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Integer getRawResult() { return result; }
//         public final void compute() {
//             final ToIntFunction<Map.Entry!(K, V)> transformer;
//             final IntBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 int r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceEntriesToIntTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsInt(r, transformer.applyAsInt(p));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceEntriesToIntTask!(K, V)
//                         t = (MapReduceEntriesToIntTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsInt(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     static final class MapReduceMappingsToIntTask!(K, V)
//         extends BulkTask<K,V,Integer> {
//         final ToIntBiFunction<? super K, ? super V> transformer;
//         final IntBinaryOperator reducer;
//         final int basis;
//         int result;
//         MapReduceMappingsToIntTask!(K, V) rights, nextRight;
//         MapReduceMappingsToIntTask
//             (BulkTask<K,V,?> p, int b, int i, int f, Node!(K, V)[] t,
//              MapReduceMappingsToIntTask!(K, V) nextRight,
//              ToIntBiFunction<? super K, ? super V> transformer,
//              int basis,
//              IntBinaryOperator reducer) {
//             super(p, b, i, f, t); this.nextRight = nextRight;
//             this.transformer = transformer;
//             this.basis = basis; this.reducer = reducer;
//         }
//         public final Integer getRawResult() { return result; }
//         public final void compute() {
//             final ToIntBiFunction<? super K, ? super V> transformer;
//             final IntBinaryOperator reducer;
//             if ((transformer = this.transformer) != null &&
//                 (reducer = this.reducer) != null) {
//                 int r = this.basis;
//                 for (int i = baseIndex, f, h; batch > 0 &&
//                          (h = ((f = baseLimit) + i) >>> 1) > i;) {
//                     addToPendingCount(1);
//                     (rights = new MapReduceMappingsToIntTask!(K, V)
//                      (this, batch >>>= 1, baseLimit = h, f, tab,
//                       rights, transformer, r, reducer)).fork();
//                 }
//                 for (Node!(K, V) p; (p = advance()) != null; )
//                     r = reducer.applyAsInt(r, transformer.applyAsInt(p.key, p.val));
//                 result = r;
//                 CountedCompleter<?> c;
//                 for (c = firstComplete(); c != null; c = c.nextComplete()) {
                    
//                     MapReduceMappingsToIntTask!(K, V)
//                         t = (MapReduceMappingsToIntTask!(K, V))c,
//                         s = t.rights;
//                     while (s != null) {
//                         t.result = reducer.applyAsInt(t.result, s.result);
//                         s = t.rights = s.nextRight;
//                     }
//                 }
//             }
//         }
//     }

//     // Unsafe mechanics
//     // private static final Unsafe U = Unsafe.getUnsafe();
//     // private static final long SIZECTL = U.objectFieldOffset(
//     //     ConcurrentHashMap.class, "sizeCtl");
//     // private static final long TRANSFERINDEX = U.objectFieldOffset(
//     //     ConcurrentHashMap.class, "transferIndex");
//     // private static final long BASECOUNT = U.objectFieldOffset(
//     //     ConcurrentHashMap.class, "baseCount");
//     // private static final long CELLSBUSY = U.objectFieldOffset(
//     //     ConcurrentHashMap.class, "cellsBusy");
//     // private static final long CELLVALUE = U.objectFieldOffset(
//     //     CounterCell.class, "value");
//     // private static final int ABASE = U.arrayBaseOffset(Node[].class);
//     // private static final int ASHIFT;

//     // static {
//     //     int scale = U.arrayIndexScale(Node[].class);
//     //     if ((scale & (scale - 1)) != 0)
//     //         throw new ExceptionInInitializerError("array index scale not a power of two");
//     //     ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);

//     //     // Reduce the risk of rare disastrous classloading in first call to
//     //     // LockSupport.park: https://bugs.openjdk.java.net/browse/JDK-8074773
//     //     Class<?> ensureLoaded = LockSupport.class;

//     //     // Eager class load observed to help JIT during startup
//     //     ensureLoaded = ReservationNode.class;
//     // }
// }