What is the ArrayDeque.addFirst method in Java?
An
is a growable array that allows us to add or remove an element from both the front and back. This class is the implementation class of the ArrayDeque Array Double Ended Queue Dequeinterface.ArrayDequecan be used as both a Stack or Queue.Nullelements are prohibited.
What is the addFirst method?
The addFirst method of the ArrayDeque class can be used to add the element to the beginning of the ArrayDeque object.
Syntax
public void addFirst(E e);
This method takes the element to be added as an argument.
This method doesn’t return any value.
Code
The code below demonstrates how to use the addFirst method.
import java.util.ArrayDeque;class AddFirst {public static void main( String args[] ) {ArrayDeque<String> arrayDeque = new ArrayDeque<>();arrayDeque.addFirst("3");System.out.println("The arrayDeque is " + arrayDeque);arrayDeque.addFirst("2");System.out.println("The arrayDeque is " + arrayDeque);arrayDeque.addFirst("1");System.out.println("The arrayDeque is " + arrayDeque);}}
Explanation
In the code above:
-
In line 1, we imported the
ArrayDequeclass. -
In line 4, we created a
ArrayDequeobject with the namearrayDeque. -
In line 5, we used the
addFirstmethod of thearrayDequeobject to add an element ("3") to the beginning of thedeque. Then, we printed it. -
In line 8, we used the
addFirstmethod to add an element ("2") to the beginning of thedeque. Then, we printed it. -
In line 11, we used the
addFirstmethod to add an element ("1") to the beginning of thedeque.
