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Showing content from https://www.geeksforgeeks.org/java/identityhashmap-size-method-in-java/ below:

IdentityHashMap size() Method in Java

Last Updated : 24 Jul, 2018

The java.util.IdentityHashMap.size() method of IdentityHashMap class is used to get the size of the IdentityHashMap which refers to the number of the key-value pair or mappings in the Map.

Syntax:

Identity_Hash_Map.size()

Parameters:

The method does not take any parameters.

Return Value:

The method returns the size of the map which also means the number of key-value pairs present in the map. Below programs illustrate the java.util.IdentityHashMap.size() method:

Program 1

Java


 // Java code to illustrate the size() 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);

        // Displaying the size of the map
        System.out.println("The size of the map is " + 
                                    identity_hash.size());
    }
}

Output:

Initial Mappings are: {Geeks=20, Welcomes=25, You=30, 4=15}
The size of the map is 4

Program 2: Java


 // Java code to illustrate the size() 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);

        // Displaying the size of the map
        System.out.println("The size of the map is " + 
                                     identity_hash.size());
    }
}

Output:

Initial Mappings are: {Welcomes=25, 4=15, You=30, Geeks=20}
The size of the map is 4

Note:

The same operation can be performed with any type of Mappings with variation and combination of different data types.

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