How does HashMap handle a null key internally?

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Question

Can we use null as a key in a HashMap? What about Hashtable?

Before diving into the question, let’s start from basics like what is Map, HashTable and the discuss their features.

What is a Map in Java?

• In Java, a Map is an object that stores key-value pairs. Each key is unique, and each key maps to exactly one value.
• There are multiple implementations of Map Interface in Java such as HashMap, LinkedHashMap, TreeMap, HashTable, ConcurrentHashMap etc.
• Each implementation has it’s own features and structure.

What is a HashMap?

• HashMap is one of the implementations of Map Interface in Java
• HashMap is part of java.util package.
• It stores data in key-value pairs and uses a hashing technique to quickly…