ArrayDeque.push(E) in Java

ArrayDeque.push(E): This method is available in java.util.ArrayDeque class of Java.

Syntax:

void java.util.ArrayDeque.push(E e)

This method takes one argument. This method pushes an element onto the stack represented by this deque.

Parameters: One parameter is required for this method.

e: the element to push.

Throws:

NullPointerException - if the specified element is null

Approach 1: When no exception

Java

import java.util.ArrayDeque;

public class ArrayDequepush {
    public static void main(String[] args) {

        ArrayDeque<Integer> arrayDeque = 
                            new ArrayDeque<Integer>();

        arrayDeque.add(1);
        arrayDeque.add(4);

        arrayDeque.push(12);
        System.out.println(arrayDeque.clone());

    }
}

Output:

[12, 1, 4]

Approach 2: NullPointerException 

Java

import java.util.ArrayDeque;

public class ArrayDequepush {
    public static void main(String[] args) {

        ArrayDeque<Integer> arrayDeque = 
                         new ArrayDeque<Integer>();

        arrayDeque.add(1);
        arrayDeque.add(4);

        arrayDeque.push(null);
        System.out.println(arrayDeque.clone());

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.util.ArrayDeque.addFirst(ArrayDeque.java:286)
	at java.base/java.util.ArrayDeque.push(ArrayDeque.java:579)