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Showing content from https://www.geeksforgeeks.org/java/abstractqueue-add-method-in-java-with-examples/ below:

AbstractQueue add() method in Java with examples

Last Updated : 11 Jul, 2025

The

add(E e)

method of

AbstractQueue

inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions. It returns true upon success and throws an

IllegalStateException

if no space is currently available.

Syntax:

public boolean add(E e)

Parameters:

This method accepts a mandatory parameter

which is the element to be inserted to the queue.

Returns:

This method returns

true

if the element is inserted in the Queue else it returns

false. Exception:

This method throws following exceptions:

IllegalStateException: if the element cannot be added at this time due to capacity restrictions
NullPointerException: if the specified element is null
ClassCastException - if the class of the specified element prevents it from being added to this queue
IllegalArgumentException - if some property of this element prevents it from being added to this queue

Below programs illustrate add() method:

Program 1: Java


 // Java program to illustrate the
// AbstractQueue add() method
import java.util.*;
import java.util.concurrent.LinkedBlockingQueue;

public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
        // Creating object of AbstractQueue<Integer>
        AbstractQueue<Integer>
            AQ = new LinkedBlockingQueue<Integer>();

        // Populating AQ
        AQ.add(10);
        AQ.add(20);
        AQ.add(30);
        AQ.add(40);
        AQ.add(50);

        // print AQ
        System.out.println("AbstractQueue contains : " + AQ);
    }
}

Output:

AbstractQueue contains : [10, 20, 30, 40, 50]

Program 2:

Program for

IllegalStateException Java


 // Java program to illustrate the
// AbstractQueue add() method
// IllegalStateException
import java.util.*;
import java.util.concurrent.LinkedBlockingQueue;

public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
        try {
            // Creating object of AbstractQueue<Integer>
            AbstractQueue<Integer>
                AQ = new LinkedBlockingQueue<Integer>(2);

            // Populating AQ
            AQ.add(10);
            AQ.add(20);
            AQ.add(30);
            AQ.add(40);
            AQ.add(50);

            // print AQ
            System.out.println("AbstractQueue contains : " + AQ);
        }
        catch (Exception e) {
            System.out.println("exception: " + e);
        }
    }
}

Output:

exception: java.lang.IllegalStateException: Queue full

Program 3:

Program for

NullPointerException Java


 // Java program to illustrate the
// AbstractQueue add() method
// NullPointerException
import java.util.*;
import java.util.concurrent.LinkedBlockingQueue;

public class GFG1 {
    public static void main(String[] argv)
        throws Exception
    {
        try {
            // Creating object of AbstractQueue<Integer>
            AbstractQueue<Integer>
                AQ = new LinkedBlockingQueue<Integer>();

            // Populating AQ
            AQ.add(10);
            AQ.add(20);
            AQ.add(30);
            AQ.add(null);
            AQ.add(50);

            // print AQ
            System.out.println("AbstractQueue contains : " + AQ);
        }
        catch (Exception e) {
            System.out.println("exception: " + e);
        }
    }
}

Output:

exception: java.lang.NullPointerException

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

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