AbstractMap.SimpleEntry hashCode() Method in Java with Examples

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:

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// 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);
        }
    }
}

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Output:

HashCode = 123
HashCode = 131
HashCode = 992

Program 2:

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// 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);
        }
    }
}

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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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