Java Map hashCode() Method (original) (raw)

Last Updated : 21 Jan, 2025

In Java, the hashCode() method is a part of the Object class and is used to generate a hash code value for an object.

**Example 1: Hash Code for Different Objects

The below Java program demonstrates that every object has a unique hashcode.

Java `

// Java program to demonstrates hashCode() // for different objects import java.io.*;

class Geeks { public static void main(String[] args) { // Create two different object Object o1 = new Object(); Object o2 = new Object();

    System.out.println("HashCode of obj1: "
                       + o1.hashCode());
    System.out.println("HashCode of obj2: "
                       + o2.hashCode());
}

}

`

Output

HashCode of obj1: 1510467688 HashCode of obj2: 868693306

**Note: The hashCode() method generates a hash code based on the objects’s memory address or internal data.

Syntax of hashCode() Method

public int hashCode()

**Return Type: This method returns an integer value that represent the hash code of the object.

**Example 2: This example demonstrates **storing key-value pair in a **HashMap and retrieving its hash code.

Java `

// Java Program to demonstrate // combined hash code for the entire map import java.util.HashMap;

public class Geeks { public static void main(String[] args) {

    HashMap<Integer, String> hm = new HashMap<>();

    hm.put(1, "Geek1");
    hm.put(2, "Geek2");
    hm.put(3, "Geek3");
   
    System.out.println("HashMap: " + hm);
  
    // Displaying the hashcode of the map
    System.out.println("HashCode of the HashMap: "
                       + hm.hashCode());
}

}

`

Output

HashMap: {1=Geek1, 2=Geek2, 3=Geek3} HashCode of the HashMap: 206037924

**Explanation: The hash code of a HashMap is calculated based on the hash codes of its key-value pairs. This ensures that two HashMap objects with identical contents will have the same hash code.