Removes the mapping for this key from this TreeMap if present.
@param key key for which mapping should be removed
@return the previous value associated with {@code key}, or
{@code null} if there was no mapping for {@code key}.
(A {@code null} return can also indicate that the map
previously associated {@code null} with {@code key}.)
@throws ClassCastException if the specified key cannot be compared
with the keys currently in the map
@throws NullPointerException if the specified key is null
and this map uses natural ordering, or its comparator
does not permit null keys
Removes the mapping for this key from this TreeMap if present.
@param key key for which mapping should be removed @return the previous value associated with {@code key}, or {@code null} if there was no mapping for {@code key}. (A {@code null} return can also indicate that the map previously associated {@code null} with {@code key}.) @throws ClassCastException if the specified key cannot be compared with the keys currently in the map @throws NullPointerException if the specified key is null and this map uses natural ordering, or its comparator does not permit null keys