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Java ArrayDeque addFirst() Method with Example

ArrayDeque Class addFirst() method: Here, we are going to learn about the addFirst() method of ArrayDeque Class with its syntax and example.
Submitted by Preeti Jain, on January 08, 2020

ArrayDeque Class addFirst() method

• addFirst() Method is available in java.lang package.
• addFirst() Method is used to add the given element at the first position of the deque.
• addFirst() Method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• addFirst() Method may throw an exception at the time of inserting an element into the deque.
  NullPointerException: This exception may throw when the given element is null exists.

Syntax:

    public void addFirst(T element);

Parameter(s):

• T element – represents the element to be inserted at the front of the deque.

Return value:

The return type of the method is void, it returns nothing.

Example:

// Java program to demonstrate the example 
// of void addFirst(T element) method of ArrayDeque 

import java.util.*;

public class AddFirstOfArrayDeque {
    public static void main(String[] args) {
        // Creating an ArrayDeque with initial capacity of
        // storing elements
        Deque < String > d_queue = new ArrayDeque < String > (10);

        // By using add() method to add elements
        // in ArrayDeque
        d_queue.add("C");
        d_queue.add("C++");
        d_queue.add("Java");
        d_queue.add("Php");
        d_queue.add("DotNet");

        // Display Deque Elements
        System.out.println("d_queue.add(): ");
        System.out.println("ArrayDeque Elements = " + d_queue);

        // By using addFirst() method to add elements at
        // the head of ArrayDeque and the sequence will be
        // like GO LANG , FORTRAN , COBOL
        d_queue.addFirst("COBOL");
        d_queue.addFirst("FORTRAN");
        d_queue.addFirst("GO LANG");

        System.out.println();

        // Display Deque Elements
        System.out.println("d_queue.addFirst(): ");
        System.out.println("ArrayDeque Elements = " + d_queue);
    }
}

Output

d_queue.add(): 
ArrayDeque Elements = [C, C++, Java, Php, DotNet]

d_queue.addFirst(): 
ArrayDeque Elements = [GO LANG, FORTRAN, COBOL, C, C++, Java, Php, DotNet]