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LinkedBlockingDeque pollFirst() method in Java
  • Last Updated : 14 Sep, 2018

The pollFirst() method of LinkedBlockingDeque 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.

Below programs illustrate pollFirst() method of LinkedBlockingDeque:



Program 1:




// Java Program Demonstrate pollFirst()
// method of LinkedBlockingDeque
  
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.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.pollFirst());
  
        // 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 pollFirst()
// 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);
  
        // Print the queue
        System.out.println("Linked Blocking Deque: " + LBD);
  
        // empty deque
        LBD.clear();
  
        System.out.println("Front element in Deque: " + LBD.pollFirst());
    }
}


Output:

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

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

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