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
