The poll() method of ConcurrentLinkedDeque 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.
Below programs illustrate poll() method of ConcurrentLinkedDeque:
Program 1:
// Java Program Demonstrate poll()// method of ConcurrentLinkedDeque  import java.util.concurrent.ConcurrentLinkedDeque;import java.util.*;  public class GFG {    public static void main(String[] args)      {          // create object of ConcurrentLinkedDeque        ConcurrentLinkedDeque<Integer> CLD            = new ConcurrentLinkedDeque<Integer>();          // Add numbers to end of ConcurrentLinkedDeque        CLD.add(7855642);        CLD.add(35658786);        CLD.add(5278367);        CLD.add(74381793);          // Print the queue        System.out.println("ConcurrentLinkedDeque: "                           + CLD);          System.out.println("Front element in Deque: "                           + CLD.poll());          // One element is deleted as poll was called        System.out.println("ConcurrentLinkedDeque: "                           + CLD);    }} |
Output:
ConcurrentLinkedDeque: [7855642, 35658786, 5278367, 74381793] Front element in Deque: 7855642 ConcurrentLinkedDeque: [35658786, 5278367, 74381793]
Program 2:
// Java Program Demonstrate poll()// method of ConcurrentLinkedDeque// when Deque is empty  import java.util.concurrent.ConcurrentLinkedDeque;import java.util.*;  public class GFG {    public static void main(String[] args)      {          // create object of ConcurrentLinkedDeque        ConcurrentLinkedDeque<Integer> CLD            = new ConcurrentLinkedDeque<Integer>();          // Add numbers to end of ConcurrentLinkedDeque        CLD.add(7855642);        CLD.add(35658786);        CLD.add(5278367);        CLD.add(74381793);          // Print the queue        System.out.println("ConcurrentLinkedDeque: "                           + CLD);          // empty deque        CLD.clear();          System.out.println("Front element in Deque: "                           + CLD.poll());    }} |
Output:
ConcurrentLinkedDeque: [7855642, 35658786, 5278367, 74381793] Front element in Deque: null
