AbstractMap.SimpleEntry hashCode() Method in Java with Examples

Last Updated : 27 Jun, 2019
AbstractMap.SimpleEntry<K, V> is used to maintain a key and a value entry. The value can be changed using the setValue method. This class facilitates the process of building custom map implementations. hashCode() method of AbstractMap.SimpleEntry<K, V> return the hash code value for this map entry. The hash code for the map entry e can be calculated by: 
(e.getKey()==null   ? 0 : e.getKey().hashCode()) ^
   (e.getValue()==null ? 0 : e.getValue().hashCode())
Syntax: 
public int hashCode()
Parameters: This method accepts nothing. Return value: This method return the hash code value for this map entry. Below programs illustrate hashCode() method: Program 1: Java 
// Java program to demonstrate
// AbstractMap.SimpleEntry.hashCode() method

import java.util.*;
import java.util.AbstractMap.SimpleEntry;

public class GFG {

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static void main(String[] args)
    {

        // create a ArrayList of Map
        ArrayList<AbstractMap
                      .SimpleEntry<Integer, Integer> >
            arrayList
            = new ArrayList<AbstractMap
                                .SimpleEntry<Integer, Integer> >();

        // add values
        arrayList.add(new AbstractMap.SimpleEntry(0, 123));
        arrayList.add(new AbstractMap.SimpleEntry(1, 130));
        arrayList.add(new AbstractMap.SimpleEntry(2, 994));

        // print keys
        for (int i = 0; i < arrayList.size(); i++) {

            // get map from list
            AbstractMap.SimpleEntry<Integer, Integer>
                map
                = arrayList.get(i);

            // get value from map using hashCode()
            int value = map.hashCode();

            System.out.println("HashCode = " + value);
        }
    }
}
Output: 
HashCode = 123
HashCode = 131
HashCode = 992
Program 2: Java 
// Java program to demonstrate
// AbstractMap.SimpleEntry.hashCode() method

import java.util.*;

public class GFG {

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static void main(String[] args)
    {

        // create a ArrayList of Map
        ArrayList<AbstractMap
                      .SimpleEntry<String, String> >
            arrayList
            = new ArrayList<AbstractMap
                                .SimpleEntry<String, String> >();

        // add values
        arrayList.add(new AbstractMap
                          .SimpleEntry(" 001AB ", " Emp 1"));
        arrayList.add(new AbstractMap
                          .SimpleEntry(" 011AC ", " Emp 2"));
        arrayList.add(new AbstractMap
                          .SimpleEntry(" 111AD ", " Emp 3"));
        arrayList.add(new AbstractMap
                          .SimpleEntry(" 101BE ", " Emp 4"));
        arrayList.add(new AbstractMap
                          .SimpleEntry(" 110CE ", " Emp 5"));

        // print keys
        for (int i = 0; i < arrayList.size(); i++) {

            // get map from list
            AbstractMap.SimpleEntry<String, String>
                map
                = arrayList.get(i);

            // get hashcode value from map using hashCode()
            int value = map.hashCode();

            System.out.println("hashCode = " + value);
        }
    }
}
Output: 
hashCode = -873386249
hashCode = -874293612
hashCode = -910934441
hashCode = -910552137
hashCode = -910906733
References: https://docs.oracle.com/javase/10/docs/api/java/util/AbstractMap.SimpleEntry.html#hashCode()
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