BlockingDeque poll() method in Java with examples

The poll() method of BlockingDeque returns the front element in the Deque container and deletes it. It returns null if the container is empty.

Syntax:

public E poll()

Parameters: This method does not accept any parameters.

Returns: This method returns front element of the Deque container if the container is not empty and deletes it. It returns null if the container is empty.

Note: The poll() method of BlockingDeque has been inherited from the LinkedBlockingDeque class in Java.

Below programs illustrate poll() method of BlockingDeque:

Program 1:

// Java Program Demonstrate poll()
// method of BlockingDeque

import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque import java.util.*;

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

    {

        // create object of BlockingDeque
        BlockingDeque<Integer> BD
            = new LinkedBlockingDeque<Integer>();

        // Add numbers to end of BlockingDeque
        BD.add(7855642);
        BD.add(35658786);
        BD.add(5278367);
        BD.add(74381793);

        // Print the queue
        System.out.println("Blocking Deque: " + BD);

        System.out.println("Front element in Deque: " + BD.poll());

        // One element is deleted as poll was called
        System.out.println("Blocking Deque: " + BD);
    }
}

Output:

Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: 7855642
Blocking Deque: [35658786, 5278367, 74381793]

Program 2:

// Java Program Demonstrate poll()
// method of BlockingDeque
// when Deque is empty

import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque import java.util.*;

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

    {

        // create object of BlockingDeque
        BlockingDeque<Integer> BD
            = new LinkedBlockingDeque<Integer>();

        // Add numbers to end of BlockingDeque
        BD.add(7855642);
        BD.add(35658786);
        BD.add(5278367);
        BD.add(74381793);

        // Print the queue
        System.out.println("Blocking Deque: " + BD);

        // empty deque
        BD.clear();

        System.out.println("Front element in Deque: " + BD.poll());
    }
}

Output:

Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: null

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#poll(long, %20java.util.concurrent.TimeUnit)