ConcurrentLinkedDeque pollFirst() method in Java

The java.util.concurrent.ConcurrentLinkedDeque.pollFirst() is an in-built method in Java which retrieves the first element of this deque and removes it. If the deque is empty, the method returns NULL.

Syntax:

Conn_Linked_Deque.pollFirst()

Parameters: This function does not accepts any parameter.

Return Values: The function returns the first element of this deque. If this deque is empty, the function returns NULL.

Below program illustrates the use of pollFirst() method:

Program 1: This program involves deque with Integer elements.

// Java Program Demonstrate pollFirst()  
// method of ConcurrentLinkedDeque    
  
import java.util.concurrent.*; 
  
class ConcurrentLinkedDequeDemo { 
    public static void main(String[] args) 
    { 
        ConcurrentLinkedDeque<Integer> cld =  
                    new ConcurrentLinkedDeque<Integer>(); 
  
        cld.addFirst(12); 
        cld.addFirst(70); 
        cld.addFirst(1009); 
        cld.addFirst(475); 
  
        // Displaying the existing LinkedDeque 
        System.out.println("Elements in"
                           + "the LinkedDeque: " + cld); 
  
        // Display and remove the first element 
        System.out.println("Element removed : "
                           + cld.pollFirst()); 
  
        // Displaying the elements 
        System.out.println("Elements in"
                           + "the LinkedDeque: " + cld); 
    } 
} 

Output:

Elements inthe LinkedDeque: [475, 1009, 70, 12]
Element removed : 475
Elements inthe LinkedDeque: [1009, 70, 12]

Program 2: This program involves deque with String elements.

// Java Program Demonstrate pollFirst()  
// method of ConcurrentLinkedDeque    
  
import java.util.concurrent.*; 
  
class ConcurrentLinkedDequeDemo { 
    public static void main(String[] args) 
    { 
        ConcurrentLinkedDeque<String> cld =  
                        new ConcurrentLinkedDeque<String>(); 
  
        cld.addFirst("GFG"); 
        cld.addFirst("Geeks"); 
        cld.addFirst("Gfg"); 
        cld.addFirst("Geeks"); 
  
        // Displaying the existing LinkedDeque 
        System.out.println("Elements in"
                           + "the LinkedDeque: " + cld); 
  
        // Display and remove the First element 
        System.out.println("Element removed : "
                           + cld.pollFirst()); 
  
        // Displaying the elements 
        System.out.println("Elements in"
                           + "the LinkedDeque: " + cld); 
    } 
} 

Output:

Elements inthe LinkedDeque: [Geeks, Gfg, Geeks, GFG]
Element removed : Geeks
Elements inthe LinkedDeque: [Gfg, Geeks, GFG]

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentLinkedDeque.html#pollFirst()

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