Introduction to Programming

Adding and maybe replace

The Map interface stores key-value pairs, also called entries, because in a Map, each key-value pair is also represented by the Entry interface, which is a nested interface of Map and thus referred as Map.Entry. 

A key-value pair or an entry can be added to a Map using the following methods:

• V put(K, V): It adds a key-value pair (or creates a key-value association). If the provided key exists already, the method overrides the old value and returns it (if the old value was null, then null is returned). If the provided key is not in the map already, the method returns null. 
• V putIfAbsent(K, V): It adds a key-value pair (or creates a key-value association). If the provided key exists already and the associated value ...