IdentityHashMap hashCode() Method in Java

Last Updated : 24 Jul, 2018

The java.util.IdentityHashMap.hashCode() method in Java is used to fetch the hash code value of a particular this IdentityHashMap. A map consists of a number of buckets to store the key-value pair. Each bucket has a unique identity and when a key-value pair is inserted into a bucket, the key’s hashcode is matched with the identifier of the bucket, and if its a match the pair is stored successfully. This is how the hash code works.

Syntax:

Identity_HashMap.hashCode()

Parameters: The method does not accept any parameters.

Return Value: The method returns the hashcode value of the map.

Below programs are used to illustrate the working of java.util.IdentityHashMap.hashCode() Method:

Program 1: Mapping String Values to Integer Keys.

// Java code to illustrate the hashCode() method
import java.util.*;
  
public class Identity_Hash_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty IdentityHashMap
        IdentityHashMap<Integer, String> identity_hash = 
                   new IdentityHashMap<Integer, String>();
  
        // Mapping string values to int keys
        identity_hash.put(10, "Geeks");
        identity_hash.put(15, "4");
        identity_hash.put(20, "Geeks");
        identity_hash.put(25, "Welcomes");
        identity_hash.put(30, "You");
  
        // Displaying the IdentityHashMap
        System.out.println("Initial Mappings are: "
                           + identity_hash);
  
        // Getting the hashcode value for the map
        System.out.println("The hashcode value of the map: "
                                + identity_hash.hashCode());
    }
}

Output:

Initial Mappings are: {10=Geeks, 30=You, 20=Geeks, 25=Welcomes, 15=4}
The hashcode value of the map: 2043437408

Program 2: Mapping Integer Values to String Keys.

// Java code to illustrate the hashCode() method
import java.util.*;
  
public class Identity_Hash_Map_Demo {
    public static void main(String[] args)
    {
  
        // Creating an empty IdentityHashMap
        Map<String, Integer> identity_hash = 
                    new IdentityHashMap<String, Integer>();
  
        // Mapping int values to string keys
        identity_hash.put("Geeks", 10);
        identity_hash.put("4", 15);
        identity_hash.put("Geeks", 20);
        identity_hash.put("Welcomes", 25);
        identity_hash.put("You", 30);
  
        // Displaying the IdentityHashMap
        System.out.println("Initial Mappings are: "
                           + identity_hash);
  
        // Getting the hashcode value for the map
        System.out.println("The hashcode value of the map: "
                                + identity_hash.hashCode());
    }
}

Output:

Initial Mappings are: {Geeks=20, Welcomes=25, You=30, 4=15}
The hashcode value of the map: 751311572

Note: The same operation can be performed with any type of Mapping with variation and combination of different data types.

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