BlockingDeque pollFirst() method in Java with examples

Last Updated : 01 Oct, 2019

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

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#pollFirst(long, %20java.util.concurrent.TimeUnit)

BlockingDeque pollLast() method in Java with examples

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