LinkedBlockingDeque pop() method in Java

The pop() method of LinkedBlockingDeque pops an element from the stack represented by this deque. In other words, it removes and returns the first element of this deque. It returns null if the container is empty.

Syntax:

public E pop()

Parameters: This method does not accept any parameters.

Returns: This method returns the element at the front of this deque (which is the top of the stack represented by this deque). It throws an NoSuchElementException if the deque is empty.

Below programs illustrate pop() method of LinkedBlockingDeque:

Program 1:

// Java Program to demonstrate pop()
// method of LinkedBlockingDeque

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

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

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

        // Add numbers to end of LinkedBlockingDeque
        LBD.addFirst(7855642);
        LBD.addFirst(35658786);
        LBD.addFirst(5278367);
        LBD.addFirst(74381793);

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

        // prints and deletes
        System.out.println("Front element in Deque: " + LBD.pop());

        // Deque after deletion of front element
        System.out.println("Linked Blocking Deque: " + LBD);
    }
}

Output:

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

Program 2:

// Java Program Demonstrate pop()
// method of LinkedBlockingDeque
// when Deque is empty

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

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

    {

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

        // Add numbers to end of LinkedBlockingDeque
        LBD.add(7855642);
        LBD.add(35658786);
        LBD.add(5278367);
        LBD.add(74381793);

        // empty deque
        LBD.clear();

        System.out.println("Front element in Deque: " + LBD.pop());
    }
}

Output:

Exception in thread "main" java.util.NoSuchElementException
    at java.util.concurrent.LinkedBlockingDeque.removeFirst(LinkedBlockingDeque.java:453)
    at java.util.concurrent.LinkedBlockingDeque.pop(LinkedBlockingDeque.java:777)
    at GFG.main(GFG.java:27)

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/LinkedBlockingDeque.html#pop()