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Showing content from https://www.geeksforgeeks.org/java/concurrentlinkeddeque-addfirst-method-in-java/ below:

ConcurrentLinkedDeque addFirst() method in Java

Last Updated : 17 Sep, 2018

The

java.util.concurrent.ConcurrentLinkedDeque.addFirst()

is an in-built function in Java which inserts the specified element at the front of the ConcurrentLinkedDeque.

Syntax:

conn_linked_deque.addFirst(elem)

Parameter:

The method accepts only a single parameter

elem

which is to be added to the beginning of the ConcurrentLinkedDeque.

Return Value:

The function has no return value.

Exception:

The method will throw

NullPointerException

when the parameter passed to the function is

null

. Due to its bounded nature, this method will never throw

IllegalStateException

or return false. Below programs illustrate the ConcurrentLinkedDeque.addFirst() method:

Program 1:

This program involves a ConcurrentLinkedDeque of Integer type.

Java


 // Java Program Demonstrate addFirst()
// 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(110);
        cld.addFirst(55);
        cld.addFirst(76);

        // Displaying the existing LinkedDeque
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld);

        // Insert a new element in the  LinkedDeque
        cld.addFirst(21);

        // Displaying the modified LinkedDeque
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld);
    }
}

Output:

Initial Elements inthe LinkedDeque: [76, 55, 110, 12]
Initial Elements inthe LinkedDeque: [21, 76, 55, 110, 12]

Program 2:

This program involves a ConcurrentLinkedDeque of Integer type with Exception Handling when

null

is passed as parameter to the function.

Java


 // Java Program Demonstrate addFirst()
// method of ConcurrentLinkedDeque 

import java.util.concurrent.*;

class ConcurrentLinkedDequeDemo {
    public static void main(String[] args)
    {
        ConcurrentLinkedDeque<String> cld = 
                         new ConcurrentLinkedDeque<String>();

        cld.addFirst("Geeks");
        cld.addFirst("Geek");
        cld.addFirst("Gfg");
        cld.addFirst("Contribute");

        // Displaying the existing LinkedDeque
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld);

        /* Exception thrown when null 
             is passed as parameter*/
        try {
            cld.addFirst(null);
        }
        catch (NullPointerException e) {
            System.out.println("NullPointerException"
                               + "thrown");
        }

        // Insert a new element in the  LinkedDeque
        cld.addFirst("Sudo Placement");

        // Displaying the modified LinkedDeque
        System.out.println("Initial Elements in"
                           + "the LinkedDeque: " + cld);
    }
}

Output:

Initial Elements inthe LinkedDeque: [Contribute, Gfg, Geek, Geeks]
NullPointerExceptionthrown
Initial Elements inthe LinkedDeque: [Sudo Placement, Contribute, Gfg, Geek, Geeks]

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

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