remove
Removes the mapping for a key from this map if it is present.
Return
the previous value associated with the key, or null if there was no mapping
Parameters
key
the key whose mapping is to be removed
Atomically removes the entry for a key only if currently mapped to the specified value.
Return
true if the value was removed
Parameters
key
the key whose mapping is to be removed
value
the value expected to be associated with the key