What is the ConcurrentLinkedQueue.size() method in Java?

ConcurrentLinkedQueue is a thread-safe, unbounded queue. The elements are ordered by FIFO (First-In-First-Out). The elements are inserted at the tail (end) and retrieved from the head (start) of the queue. null elements are not allowed in the queue. We can use ConcurrentLinkedQueue when multiple threads share a single queue.

The size method can be used to get the number of elements present in the ConcurrentLinkedQueue object.

Syntax

public int size()

Parameters

This method doesn’t take any parameters.

Return value

The size method returns an integer value that represents the number of elements present in the queue object.

Code

The code below demonstrates how to use the size method.

import java.util.concurrent.ConcurrentLinkedQueue;
class Size {
    public static void main( String args[] ) {
      ConcurrentLinkedQueue<String> queue = new ConcurrentLinkedQueue<>();
      queue.add("1");
      queue.add("2");
      queue.add("3");
      System.out.println("The queue is " + queue);
      System.out.println("The size of the queue is " + queue.size());
    }
}

Explanation

In the code above:

  • In line 1: We import the ConcurrentLinkedQueue class.

  • In line 4: We create a ConcurrentLinkedQueue object with the name queue.

  • From lines 5 to 7: We use the add() method of the queue object to add three elements ("1","2","3") to queue.

  • In line 10: We use the size() method of the queue object to get the number of elements present in the queue. In our case, 3 will be returned.

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