BlockingDeque poll() method in Java with examples

Last Updated : 01 Oct, 2019

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

// 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

// 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)

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