Removes and returns a key-value mapping associated with the least key in this map, or {@code null} if the map is empty.
@return the removed first entry of this map, or {@code null} if this map is empty
See Implementation
Removes and returns a key-value mapping associated with the least key in this map, or {@code null} if the map is empty.
@return the removed first entry of this map, or {@code null} if this map is empty