IdentityHashMap keySet() Method in Java

Last Updated : 24 Jul, 2018
The java.util.IdentityHashMap.keySet() method in Java is used to create a set out of the key elements contained in the hash map. It basically returns a set view of the keys or we can create a new set and store the key elements in them. Syntax: 
Identity_Hash_Map.keySet()
Parameters: The method does not take any parameter. Return Value: The method returns a set having the keys of the Identity hash map. Below programs are used to illustrate the working of java.util.IdentityHashMap.keySet() Method: Program 1: Mapping String Values to Integer Keys. Java 
// Java code to illustrate the keySet() method
import java.util.*;

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

        // Creating an empty IdentityHashMap
        Map<Integer, String> Identity_hash = new IdentityHashMap<Integer, String>();

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

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

        // Using keySet() to get the set view of keys
        System.out.println("The set is: " + Identity_hash.keySet());
    }
}
Output: 
Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
The set is: [30, 15, 10, 25, 20]
Program 2: Mapping Integer Values to String Keys. Java 
// Java code to illustrate the keySet() method
import java.util.*;

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

        // Creating an empty IdentityHashMap
        Map<String, Integer> Identity_hash = new IdentityHashMap<String, Integer>();

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

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

        // Using keySet() to get the set view of keys
        System.out.println("The set is: " + Identity_hash.keySet());
    }
}
Output: 
Initial Mappings are: {Welcomes=25, 4=15, You=30, Geeks=20}
The set is: [Welcomes, 4, You, Geeks]
Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.
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