Java ArrayDeque Class: addFirst() Method

public void addFirst(E e)

The addFirst() method is used to insert an given element at the front of this deque.

Package: java.util

Java Platform: Java SE 8

Syntax:

addFirst(E e)

Parameters:

Return Value Type: void

Throws:

NullPointerException - if the specified element is null

Pictorial Presentation

Example: Java ArrayDeque Class: addFirst() Method

import java.util.ArrayDeque;
import java.util.Deque;

public class Main {
   public static void main(String[] args) {
      
      // Create an empty array deque with an initial capacity 3
      Deque<Integer> deque = new ArrayDeque<Integer>(3);

      // Use add() method to add elements in the deque
      deque.add(40);
      deque.add(50);
      deque.add(60);

      // Use addFirst() method to add 3 elements 
      // at the front of the deque and print all the elements
      deque.addFirst(30);
       for (Integer number : deque) {
         System.out.println("Number = " + number);
       }
      deque.addFirst(20);
      System.out.println();
       for (Integer number : deque) {
         System.out.println("Number = " + number);
       }
      deque.addFirst(10);
      System.out.println();
       for (Integer number : deque) {
         System.out.println("Number = " + number);
      }
  }
}

Output:

 
Number = 30
Number = 40
Number = 50
Number = 60


Number = 20
Number = 30
Number = 40
Number = 50
Number = 60


Number = 10
Number = 20
Number = 30
Number = 40
Number = 50
Number = 60

Java Code Editor:

Previous:add Method
Next:addLast Method