Returns a view of the portion of this map whose keys are
strictly less than {@code toKey}. The returned map is backed
by this map, so changes in the returned map are reflected in
this map, and vice-versa. The returned map supports all
optional map operations that this map supports.
<p>The returned map will throw an {@code IllegalArgumentException}
on an attempt to insert a key outside its range.
@param toKey high endpoint (exclusive) of the keys in the returned map
@return a view of the portion of this map whose keys are strictly
less than {@code toKey}
@throws ClassCastException if {@code toKey} is not compatible
with this map's comparator (or, if the map has no comparator,
if {@code toKey} does not implement {@link Comparable}).
Implementations may, but are not required to, throw this
exception if {@code toKey} cannot be compared to keys
currently in the map.
@throws NullPointerException if {@code toKey} is null and
this map does not permit null keys
@throws IllegalArgumentException if this map itself has a
restricted range, and {@code toKey} lies outside the
bounds of the range
Returns a view of the portion of this map whose keys are strictly less than {@code toKey}. The returned map is backed by this map, so changes in the returned map are reflected in this map, and vice-versa. The returned map supports all optional map operations that this map supports.
<p>The returned map will throw an {@code IllegalArgumentException} on an attempt to insert a key outside its range.
@param toKey high endpoint (exclusive) of the keys in the returned map @return a view of the portion of this map whose keys are strictly less than {@code toKey} @throws ClassCastException if {@code toKey} is not compatible with this map's comparator (or, if the map has no comparator, if {@code toKey} does not implement {@link Comparable}). Implementations may, but are not required to, throw this exception if {@code toKey} cannot be compared to keys currently in the map. @throws NullPointerException if {@code toKey} is null and this map does not permit null keys @throws IllegalArgumentException if this map itself has a restricted range, and {@code toKey} lies outside the bounds of the range