ArrayDeque addFirst() Method in Java
Last Updated :
10 Dec, 2018
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The java.util.ArrayDeque.addFirst(Object element) method in Java is used to insert a specific element at the front of this deque.
Syntax:
Java
Java
Array_Deque.addFirst(Object element)Parameters: The parameter element is of the type ArrayDeque and refers to the element to be added. Return Value: The function does not return any value. Exceptions: The method throws NullPointerException if the passed parameter is NULL. Below programs illustrate the Java.util.ArrayDeque.addFirst() method: Program 1:
// Java code to illustrate addFirst()
import java.util.*;
public class ArrayDequeDemo {
public static void main(String args[])
{
// Creating an empty ArrayDeque
Deque<Integer> de_que = new ArrayDeque<Integer>();
// Use add() method to add elements into the Deque
de_que.add(10);
de_que.add(15);
de_que.add(30);
de_que.add(20);
de_que.add(5);
// Displaying the ArrayDeque
System.out.println("ArrayDeque: " + de_que);
// Adding elements at front
de_que.addFirst(40);
de_que.addFirst(50);
de_que.addFirst(60);
de_que.addFirst(70);
// Displaying the ArrayDeque
System.out.println("ArrayDeque_front_addition: " + de_que);
// Adding elements using add()
de_que.add(1);
de_que.add(2);
de_que.add(3);
// Displaying the final ArrayDeque
System.out.println("Final ArrayDeque: " + de_que);
}
}
Output:
Program 2:
ArrayDeque: [10, 15, 30, 20, 5] ArrayDeque_front_addition: [70, 60, 50, 40, 10, 15, 30, 20, 5] Final ArrayDeque: [70, 60, 50, 40, 10, 15, 30, 20, 5, 1, 2, 3]
// Java code to illustrate addFirst()
import java.util.*;
public class ArrayDequeDemo {
public static void main(String args[])
{
// Creating an empty ArrayDeque
Deque<String> de_que = new ArrayDeque<String>();
// Use add() method to add elements into the Deque
de_que.add("Welcome");
de_que.add("To");
de_que.add("Geeks");
de_que.add("4");
de_que.add("Geeks");
// Displaying the ArrayDeque
System.out.println("ArrayDeque: " + de_que);
// Adding elements at front
de_que.addFirst("GFG");
de_que.addFirst("World");
de_que.addFirst("Hello");
// Displaying the ArrayDeque
System.out.println("ArrayDeque_front_addition: " + de_que);
// Adding elements using add()
de_que.add("Coding");
de_que.add("At");
de_que.add("BEST");
// Displaying the final ArrayDeque
System.out.println("Final ArrayDeque: " + de_que);
}
}
Output:
ArrayDeque: [Welcome, To, Geeks, 4, Geeks] ArrayDeque_front_addition: [Hello, World, GFG, Welcome, To, Geeks, 4, Geeks] Final ArrayDeque: [Hello, World, GFG, Welcome, To, Geeks, 4, Geeks, Coding, At, BEST]
