AddFirst() Method : Insert element at start ArrayDeque in Java

Declaration :

public void addFirst(E e)

1	public void addFirst(E e)

Explanation :

Purpose	The java.util.ArrayDeque.addFirst(E e) method inserts the specified element E at the front of the deque.
Parameters	e ===> The element to be added in the deque.
Return Value	This method does not return any value.
Exception	NullPointerException — if the specified element is null.

Java Program : Example

Below example will explain java.util.ArrayDeque.addFirst(E) method.

package com.c4learn;
import java.util.ArrayDeque;
import java.util.Deque;
public class ArrayDequeDemo {
   public static void main(String[] args) {
      // Create empty array deque with an initial capacity
      Deque<Integer> deque = new ArrayDeque<Integer>(8);
      // Use add() method to add elements
      deque.add(100);
      deque.add(200);
      deque.add(300);
      deque.add(400);        
      deque.add(500);        
      // Use addFirst() method to add elements
      deque.addFirst(111);  
      deque.addFirst(222);  
      deque.addFirst(333);
      // Print all the elements available in deque
      for (Integer number : deque) {
         System.out.println("Element is " + number);
      } 
   }
}

package com.c4learn;

import java.util.ArrayDeque;

import java.util.Deque;

public class ArrayDequeDemo {

public static void main(String[] args) {

// Create empty array deque with an initial capacity

Deque<Integer> deque = new ArrayDeque<Integer>(8);

// Use add() method to add elements

deque.add(100);

deque.add(200);

deque.add(300);

deque.add(400);

deque.add(500);

// Use addFirst() method to add elements

deque.addFirst(111);

deque.addFirst(222);

deque.addFirst(333);

// Print all the elements available in deque

for (Integer number : deque) {

System.out.println("Element is " + number);

}

Output of Program :

Element is 333
Element is 222
Element is 111
Element is 100
Element is 200
Element is 300
Element is 400
Element is 500

Element is 333

Element is 222

Element is 111

Element is 100

Element is 200

Element is 300

Element is 400

Element is 500