equals() vs compareTo() methods

In this post, we will learn the difference between "equals()" and "compareTo()" methods in Java. This is a frequently asked question in Java interviews for beginners. Let's dive into it.

Difference between "equals()" and "compareTo()" methods in Java

Feature equals() method compareTo() method
Defined in Defined in the Object class. Defined in the Comparable interface.
Method signature public boolean equals(Object obj) public int compareTo(T obj)
Purpose Used to check if two objects are equal. Used to compare two objects for ordering.
Return Type Returns a boolean (true if objects are equal, false otherwise). Returns an integer (negative, zero, or positive).
Method Parameters Takes an Object type as a parameter, and requires casting to the specific class type for comparisons. Takes a parameter of the same class type as the implementing class.
Natural Ordering Generally overridden for specific class types to define equality based on their properties. Generally overridden to provide natural ordering of objects.
Implementation Developer-defined for custom object comparisons. Developer-defined for custom object comparisons.
Relation with equals() It's recommended to override "equals()" whenever you override "compareTo()", to ensure consistency between equality and ordering. If "compareTo()" is not defined or inconsistent with "equals()", sorting methods may not work as expected.
Interface Dependency Not required to implement any interface. Required to implement the Comparable<T> interface.
Use in Collections Used by certain collection classes like HashSet and HashMap to determine object uniqueness. Used by collection classes like TreeSet and TreeMap to sort elements.


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