Returns {@code true} if this map contains a mapping for the specified
key.
@param key key whose presence in this map is to be tested
@return {@code true} if this map contains a mapping for the
specified 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
Returns {@code true} if this map contains a mapping for the specified key.
@param key key whose presence in this map is to be tested @return {@code true} if this map contains a mapping for the specified 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