The remove$($k$,$v$)$ method is used to remove an entry from a map. This method spends time to locate an existing item with the given key. Write an efficient version of this method, removeOnlyIfNull$($k$,$v$),$ that removes the entry from the map only if there is null value with a key k$.$

Provide Java implementation of removeOnlyIfNull$($k$,$v$)$ method for the UnSortedTableMap class. Write the testing code in the main method.

Hint: Your solution should check if the value associated with key is null then remove, otherwise return the existing value and say value not null $.$