BlockingDeque pollFirst() method in Java with examples
The pollFirst() 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 pollFirst()
Parameters: This method does not accept any parameters.
Returns: This method returns front element in the Deque container if the container is not empty and deletes the element. It returns null if the container is empty.
Note: The pollFirst() method of BlockingDeque has been inherited from the LinkedBlockingDeque class in Java.
Below programs illustrate pollFirst() method of BlockingDeque:
Program 1:
// Java Program Demonstrate pollFirst()// 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.addFirst(7855642);        BD.addFirst(35658786);        BD.addFirst(5278367);        BD.addFirst(74381793);          // Print the queue        System.out.println("Blocking Deque: " + BD);          // prints and deletes        System.out.println("Front element in Deque: " + BD.pollFirst());          // Deque after deletion of front element        System.out.println("Blocking Deque: " + BD);    }} |
Output:
Blocking Deque: [74381793, 5278367, 35658786, 7855642] Front element in Deque: 74381793 Blocking Deque: [5278367, 35658786, 7855642]
Program 2:
// Java Program Demonstrate pollFirst()// 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 LinkedBlockingDeque        LinkedBlockingDeque<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.pollFirst());    }} |
Output:
Blocking Deque: [7855642, 35658786, 5278367, 74381793] Front element in Deque: null
