AbstractMap.SimpleEntry getKey() 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. getKey() method of AbstractMap.SimpleEntry<K, V> returns the key corresponding to this entry. 

Syntax:

public K getKey()

Parameters: This method accepts nothing. 

Return value: This method returns the key corresponding to this entry. 

Below programs illustrate getKey() method: 

Program 1:

Java

// Java program to demonstrate
// AbstractMap.SimpleEntry.getKey() 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 key from map.getKey();
            int key = map.getKey();

            System.out.println("Key " + key);
        }
    }
}

Output:

Key 0
Key 1
Key 2

Program 2:

Java

// Java program to demonstrate
// AbstractMap.SimpleEntry.getkey() 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 key from map.getKey()
            String key = map.getKey();

            System.out.println("Key " + key);
        }
    }
}

Output:

Key  001AB 
Key  011AC 
Key  111AD 
Key  101BE 
Key  110CE

References: https://docs.oracle.com/javase/10/docs/api/java/util/AbstractMap.SimpleEntry.html#getKey()