What is the ArrayBlockingQueue.peek method in Java?

ArrayBlockingQueue is a bounded queue and it is thread-safe. Internally, it uses a fixed-size array. Once the object is created, the size cannot be changed. The elements of this queue follow First-In-First-OutElements are inserted at the end of the queue and retrieved from the head of the queue.. Also, null objects are not allowed as elements.

The peek method can be used to get the head element (first element) of the ArrayBlockingQueue object.

Syntax

public E peek()

Parameters

This method doesn’t take any argument.

Return value

This method returns the head element of the queue. If the queue is empty, then null is returned.

Code

The code below demonstrates how to use the peek method.

import java.util.concurrent.ArrayBlockingQueue;
class PeekDemo {
    public static void main( String args[] ) {
      ArrayBlockingQueue<String> queue = new ArrayBlockingQueue<>(5);
      queue.add("1");
      queue.add("2");
      queue.add("3");
      System.out.println("The queue is " + queue);
      System.out.println("queue.peek() - " + queue.peek());
    }
}

Explanation

In the above code:

  • We imported the ArrayBlockingQueue from the java.util.concurrent package.

  • We created an object for the ArrayBlockingQueue class with the name queue and size 5.

  • We used the add method to add three elements to the queue object.

  • We used the peek method to get the head element of the queue.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)