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Java Queue example

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Queue Interface is part of java.util package. Queue generally works on FIFO (First In First Out) in ordering elements. In FIFO, new element is added at the end while in other cases ordering properties has to be specified. Queues are bounded which means that number of elements are restricted in it.

Queue Interface is part of java.util package. Queue generally works on FIFO (First In First Out) in ordering elements. In FIFO, new element is added at the end while in other cases ordering properties has to be specified. Queues are bounded which means that number of elements are restricted in it.

add() method is used to insert an element in the queue but it will throw an exception if the operation fails.

offer() method is also used to insert an element in the queue but it will return false if the operation fails.

remove() method returns and removes the head of the queue. It throws an exception if the operation fails.

poll() method returns and removes the head of this queue. It return null if the operation fails.

element() method returns the head of the queue. It throws an exception if the operation fails.

peek() method returns the head of the queue. It return null if the operation fails.

In the following example we will implement Queue by its subclass LinkedList. add()and offer() methods are used to add elements o LinkedList while remove() and poll() methods are used to remove elements.

Following is the Java queue example:

import java.util.LinkedList;
import java.util.Queue;

public class MainDemo {

    public void queueExample() {

        Queue queue = new LinkedList();

        queue.add("Java");
        queue.add("DotNet");

        queue.offer("PHP");
        queue.offer("HTML");

        System.out.println("remove: " + queue.remove());
        System.out.println("element: " + queue.element());
        System.out.println("poll: " + queue.poll());
        System.out.println("peek: " + queue.peek());

    }

    public static void main(String[] args) {
        new MainDemo().queueExample();
    }
}

Output:

remove: Java
element: DotNet
poll: DotNet
peek: PHP

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Posted on: May 13, 2013

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