The java.util.Map.entrySet() method in Java is used to create a set out of the same elements contained in the map. It basically returns a set view of the map or we can create a new set and store the map elements into them.
Syntax:
map.entrySet()
Parameters: The method does not take any parameter.
Return Value: The method returns a set having same elements as the hash map.
Below programs illustrate the java.util.Map.entrySet() Method:
Program 1: Mapping String Values to Integer Keys.
// Java code to illustrate the entrySet() method  import java.util.*;  public class Map_Demo {    public static void main(String[] args)    {        // Creating an empty Map        Map<Integer, String> map = new HashMap<Integer, String>();          // Mapping string values to int keys        map.put(10, "Geeks");        map.put(15, "4");        map.put(20, "Geeks");        map.put(25, "Welcomes");        map.put(30, "You");          // Displaying the Map        System.out.println("Initial Mappings are: " + map);          // Using entrySet() to get the set view        System.out.println("The set is: " + map.entrySet());    }} |
Output:
Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The set is: [20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4]
Program 2: Mapping Integer Values to String Keys.
// Java code to illustrate the entrySet() methodimport java.util.*;  public class Map_Demo {    public static void main(String[] args)    {        // Creating an empty Map        Map<String, Integer> map = new HashMap<String, Integer>();          // Mapping int values to string keys        map.put("Geeks", 10);        map.put("4", 15);        map.put("Geeks", 20);        map.put("Welcomes", 25);        map.put("You", 30);          // Displaying the Map        System.out.println("Initial Mappings are: " + map);          // Using entrySet() to get the set view        System.out.println("The set is: " + map.entrySet());    }} |
Output:
Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
The set is: [4=15, Geeks=20, You=30, Welcomes=25]
Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.
Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Map.html#entrySet()
