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Set hashCode() Method in Java

Last Updated : 11 Jul, 2025
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In Java, the hashCode() method is defined in the Object class and is used to generate a hash code for objects. It plays a very important role in hash-based collections like HashMap, HashSet, and HashTable.

Example 1: This example demonstrates how hashCode() is used to get the hash code of the HashSet.

Java 
// Java Program to demonstrate the working of 
// hashCode() method in Set 
import java.util.*; 

public class Geeks { 
	public static void main(String[] args) 
	{ 
		// creating an Set 
		Set<Integer> s = new HashSet<Integer>(); 

		// using add() to insert elements
		s.add(1); 
		s.add(2); 
		s.add(3); 
		s.add(4); 

		System.out.println("Set: " + s); 

		// Get the hashCode value 
		// using hashCode() value 
		System.out.println("HashCode value: " 
		+ s.hashCode()); 
	} 
}

Output
Set: [1, 2, 3, 4]
HashCode value: 10

Syntax of hashCode() Method

public int hashCode()

  • Parameter: This method does not take any parameter.
  • Return Type: This method return an int value.

Example 2: This example demonstrates that without overriding hashCode(), different objects with similar data have different hash codes.

Java 
// Java program to demonstrates hashcode()
// value for different objects
class Geeks {
    int id;
    String name;

    public Geeks(int id, String name)
    {
        this.id = id;
        this.name = name;
    }

    public static void main(String[] args)
    {
        Geeks obj1 = new Geeks(1, "John");
        Geeks obj2 = new Geeks(1, "John");

        System.out.println("hashCode of obj1: "
                           + obj1.hashCode());
        System.out.println("hashCode of obj2: "
                           + obj2.hashCode());
    }
}

Output
hashCode of obj1: 1510467688
hashCode of obj2: 868693306

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