ConcurrentLinkedQueue add() method in Java

The add() method of ConcurrentLinkedQueue is used to insert the element, passed as parameter to add() of ConcurrentLinkedQueue, at the tail of this ConcurrentLinkedQueue. This method returns True if insertion is successful. ConcurrentLinkedQueue is unbounded, so this method will never throw IllegalStateException or return false.

Syntax:

public boolean add(E e)

Parameter: This method takes a single parameter e which represents the element to be insert into this ConcurrentLinkedQueue.

Returns: This method returns true after successful insertion of element.

Exception: This method throws NullPointerException if the specified element is null.

Below programs illustrate add() method of ConcurrentLinkedQueue:

Example 1: To demonstrate add() method of ConcurrentLinkedQueue to add String.

// Java Program Demonstrate add()
// method of ConcurrentLinkedQueue

import java.util.concurrent.*;

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

        // create an ConcurrentLinkedQueue
        ConcurrentLinkedQueue<String>
            queue = new ConcurrentLinkedQueue<String>();

        // Add String to queue
        queue.add("Kolkata");
        queue.add("Patna");
        queue.add("Delhi");
        queue.add("Jammu");

        // Displaying the existing ConcurrentLinkedQueue
        System.out.println("ConcurrentLinkedQueue: " + queue);
    }
}

Output:

ConcurrentLinkedQueue: [Kolkata, Patna, Delhi, Jammu]

Example 2: To demonstrate add() method of ConcurrentLinkedQueue for adding Numbers.

// Java Program Demonstrate add()
// method of ConcurrentLinkedQueue

import java.util.concurrent.*;

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

        // create an ConcurrentLinkedQueue
        ConcurrentLinkedQueue<Integer>
            queue = new ConcurrentLinkedQueue<Integer>();

        // Add Numbers to queue
        queue.add(4353);
        queue.add(7824);
        queue.add(78249);
        queue.add(8724);

        // Displaying the existing ConcurrentLinkedQueue
        System.out.println("ConcurrentLinkedQueue: " + queue);
    }
}

Output:

ConcurrentLinkedQueue: [4353, 7824, 78249, 8724]

Example 3: To demonstrate NullPointerException thrown by add() method for adding Null.

// Java Program Demonstrate add()
// method of ConcurrentLinkedQueue

import java.util.concurrent.*;

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

        // create an ConcurrentLinkedQueue
        ConcurrentLinkedQueue<Integer>
            queue = new ConcurrentLinkedQueue<Integer>();

        // Add null to queue
        try {
            queue.add(null);
        }
        catch (NullPointerException e) {
            System.out.println("Exception thrown "
                               + "while adding null: " + e);
        }
    }
}

Output:

Exception thrown while adding null: java.lang.NullPointerException

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedQueue.html#add-E-