Constructs a new, empty tree map, ordered according to the given
comparator. All keys inserted into the map must be <em>mutually
comparable</em> by the given comparator: {@code comparator.compare(k1,
k2)} must not throw a {@code ClassCastException} for any keys
{@code k1} and {@code k2} in the map. If the user attempts to put
a key into the map that violates this constraint, the {@code put(Object
key, Object value)} call will throw a
{@code ClassCastException}.
@param comparator the comparator that will be used to order this map.
If {@code null}, the {@linkplain Comparable natural
ordering} of the keys will be used.
Constructs a new, empty tree map, ordered according to the given comparator. All keys inserted into the map must be <em>mutually comparable</em> by the given comparator: {@code comparator.compare(k1, k2)} must not throw a {@code ClassCastException} for any keys {@code k1} and {@code k2} in the map. If the user attempts to put a key into the map that violates this constraint, the {@code put(Object key, Object value)} call will throw a {@code ClassCastException}.
@param comparator the comparator that will be used to order this map. If {@code null}, the {@linkplain Comparable natural ordering} of the keys will be used.