AbstractMap hashCode() Method in Java with Examples

The AbstractMap.hashCode() method in Java is used to fetch the hash code value of a particular this AbstractMap. 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:

AbstractMap.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 AbstractMap.hashCode() Method:

Program 1: Mapping String Values to Integer Keys.

// Java code to illustrate the hashCode() method

import java.util.*;

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

        // Creating an empty AbstractMap
        AbstractMap<Integer, String>
            abs_map = new IdentityHashMap<Integer, String>();

        // Mapping string values to int keys
        abs_map.put(10, "Geeks");
        abs_map.put(15, "4");
        abs_map.put(20, "Geeks");
        abs_map.put(25, "Welcomes");
        abs_map.put(30, "You");

        // Displaying the AbstractMap
        System.out.println("Initial Mappings are: "
                           + abs_map);

        // Getting the hashcode value for the map
        System.out.println("The hashcode value of the map: "
                           + abs_map.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 Abstract_Map_Demo {
    public static void main(String[] args)
    {

        // Creating an empty AbstractMap
        AbstractMap<String, Integer>
            abs_hash = new IdentityHashMap<String, Integer>();

        // Mapping int values to string keys
        abs_hash.put("Geeks", 10);
        abs_hash.put("4", 15);
        abs_hash.put("Geeks", 20);
        abs_hash.put("Welcomes", 25);
        abs_hash.put("You", 30);

        // Displaying the AbstractMap
        System.out.println("Initial Mappings are: "
                           + abs_hash);

        // Getting the hashcode value for the map
        System.out.println("The hashcode value of the map: "
                           + abs_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.