Equals and Hash Code in Java

Introduction

The Java super class java.lang.Object has two very important methods defined in it. They are -

• public boolean equals(Object obj)
• public int hashCode()

These methods prove very important when user classes are confronted with other Java classes, when objects of such classes are added to collections etc. These two methods have become part of Sun Certified Java Programmer 1.4 exam (SCJP 1.4) objectives. This article intends to provide the necessary information about these two methods that would help the SCJP 1.4 exam aspirants. Moreover, this article hopes to help you understand the mechanism and general contracts of these two methods; irrespective of whether you are interested in taking the SCJP 1.4 exam or not. This article should help you while implementing these two methods in your own classes.

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