ConcurrentLinkedDeque pollFirst() method in Java

Last Updated : 26 Nov, 2018

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

// 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

// 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()

ConcurrentLinkedDeque removeFirst() method in Java

RICHIK BHATTACHARJEE

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