ConcurrentHashMap size() Method in Java

The java.util.concurrent.ConcurrentHashMap.size() method is an in-built function in Java which counts the number of key-value mappings in this map and returns the integer value.

Syntax:

public int size()

Return Value: The function returns an integer value which denotes the number of key-value mappings in this map.

Below program illustrate the use of size() method :

Program 1:

// Java Program Demonstrate size()
// method of ConcurrentHashMap

import java.util.concurrent.*;

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

        ConcurrentHashMap<Integer, String>
            chm = new ConcurrentHashMap<Integer, String>();

        chm.put(100, "Geeks");
        chm.put(101, "for");
        chm.put(102, "Geeks");

        // Display the number of
        // key-value mappings
        System.out.println("The number of "
                           + "key-value mappings is "
                           + chm.size());
    }
}

Output:

The number of key-value mappings is 3

Program 2:

// Java Program Demonstrate size()
// method of ConcurrentHashMap

import java.util.concurrent.*;

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

        ConcurrentHashMap<Integer, Integer>
            chm = new ConcurrentHashMap<Integer, Integer>();

        chm.put(1, 100);
        chm.put(2, 200);
        chm.put(3, 300);
        chm.put(4, 400);
        chm.put(5, 500);
        chm.put(6, 600);

        // Display the number of
        // key-value mappings
        System.out.println("The number of "
                           + "key-value mappings is "
                           + chm.size());
    }
}

Output:

The number of key-value mappings is 6

Reference : https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentHashMap.html#size()