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Showing content from https://www.geeksforgeeks.org/java/queue-offer-method-in-java/ below:

Queue offer() method in Java

Last Updated : 11 Jul, 2025

The

offer(E e)

method of

Queue Interface

inserts the specified element into this queue if it is possible to do so immediately without violating capacity restrictions. This method is preferable to

add()

method since this method does not throws an exception when the capacity of the container is full since it returns false.

Syntax:

boolean offer(E e)

Parameters:

This method accepts a mandatory parameter

which is the element to be inserted in the Queue.

Returns:

This method returns true on successful insertion else it returns false.

Exceptions:

The function throws four exceptions which are described as below:

ClassCastException: when the class of the element to be entered prevents it from being added to this container.
IllegalArgumentException: when some property of the element prevents it to be added to the queue.
NullPointerException: when the element to be inserted is passed as null and the Queue's interface does not allow null elements.

Below programs illustrate offer() method of Queue:

Program 1:

With the help of

LinkedBlockingDeque

Java


 // Java Program Demonstrate offer()
// method of Queue

import java.util.*;
import java.util.concurrent.LinkedBlockingQueue;

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

        // create object of Queue
        Queue<Integer> Q
            = new LinkedBlockingQueue<Integer>(3);

        if (Q.offer(10))
            System.out.println("The Queue is not full"
                               + " and 10 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(15))
            System.out.println("The Queue is not full"
                               + " and 15 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(25))
            System.out.println("The Queue is not full"
                               + " and 25 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(20))
            System.out.println("The Queue is not full"
                               + " and 20 is inserted");
        else
            System.out.println("The Queue is full");

        // before removing print Queue
        System.out.println("Queue: " + Q);
    }
}

Output:

The Queue is not full and 10 is inserted
The Queue is not full and 15 is inserted
The Queue is not full and 25 is inserted
The Queue is full
Queue: [10, 15, 25]

Program 2:

With the help of

ConcurrentLinkedDeque

Java


 // Java Program Demonstrate offer()
// method of Queue

import java.util.*;
import java.util.concurrent.ConcurrentLinkedDeque;

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

        // create object of Queue
        Queue<Integer> Q
            = new ConcurrentLinkedDeque<Integer>();

        if (Q.offer(10))
            System.out.println("The Queue is not full"
                               + " and 10 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(15))
            System.out.println("The Queue is not full"
                               + " and 15 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(25))
            System.out.println("The Queue is not full"
                               + " and 25 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(20))
            System.out.println("The Queue is not full"
                               + " and 20 is inserted");
        else
            System.out.println("The Queue is full");

        // before removing print Queue
        System.out.println("Queue: " + Q);
    }
}

Output:

The Queue is not full and 10 is inserted
The Queue is not full and 15 is inserted
The Queue is not full and 25 is inserted
The Queue is not full and 20 is inserted
Queue: [10, 15, 25, 20]

Program 3:

With the help of

ArrayDeque

Java


 // Java Program Demonstrate offer()
// method of Queue

import java.util.*;

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

        // create object of Queue
        Queue<Integer> Q
            = new ArrayDeque<Integer>(6);

        if (Q.offer(10))
            System.out.println("The Queue is not full"
                               + " and 10 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(15))
            System.out.println("The Queue is not full"
                               + " and 15 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(25))
            System.out.println("The Queue is not full"
                               + " and 25 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(20))
            System.out.println("The Queue is not full"
                               + " and 20 is inserted");
        else
            System.out.println("The Queue is full");

        // before removing print Queue
        System.out.println("Queue: " + Q);
    }
}

Output:

The Queue is not full and 10 is inserted
The Queue is not full and 15 is inserted
The Queue is not full and 25 is inserted
The Queue is not full and 20 is inserted
Queue: [10, 15, 25, 20]

Program 4:

With the help of

LinkedList

Java


 // Java Program Demonstrate offer()
// method of Queue

import java.util.*;

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

        // create object of Queue
        Queue<Integer> Q
            = new LinkedList<Integer>();

        if (Q.offer(10))
            System.out.println("The Queue is not full"
                               + " and 10 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(15))
            System.out.println("The Queue is not full"
                               + " and 15 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(25))
            System.out.println("The Queue is not full"
                               + " and 25 is inserted");
        else
            System.out.println("The Queue is full");

        if (Q.offer(20))
            System.out.println("The Queue is not full"
                               + " and 20 is inserted");
        else
            System.out.println("The Queue is full");

        // before removing print Queue
        System.out.println("Queue: " + Q);
    }
}

Output:

The Queue is not full and 10 is inserted
The Queue is not full and 15 is inserted
The Queue is not full and 25 is inserted
The Queue is not full and 20 is inserted
Queue: [10, 15, 25, 20]

Below programs illustrate

exceptions thrown by this method

Program 5:

To show

NullPointerException

Java


 // Java Program Demonstrate offer()
// method of Queue when Null is passed

import java.util.*;
import java.util.concurrent.LinkedBlockingQueue;

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

        // create object of Queue
        Queue<Integer> Q
            = new LinkedBlockingQueue<Integer>();

        // Add numbers to end of Deque
        Q.offer(7855642);
        Q.offer(35658786);
        Q.offer(5278367);

        try {
            // when null is inserted
            Q.offer(null);
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Exception: java.lang.NullPointerException

Note:

The other two exceptions are internal and are caused depending on the compiler hence cannot be shown in the code.

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

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