Introduction In this Java HashMap example I am going to tell you how to use custom object as a key in HashMap. In custom object as a key in HashMap example, I will show you how to work with user defined objects as keys in Map. To use user defined objects as keys in Map…

What is HashSet HashSet extends AbstractSet and is an implementation of Set interface. HashSet also implements Serializable and Cloneable interfaces. HashSet is backed by hash table(actually HashMap instance), i.e., the HashSet uses hash table(HashMap) to store collection elements. Like HashMap, it allows null only one element.

Introduction Here I will discuss how to override equals() and hashCode() methods in Java. In Java language the important contract is whenever you override one of the methods (equals() and hashCode()), then you must override the other method. So it means that when you override method equals() then you must override hashCode() or vice versa.