ArrayDeque.addAll(Collection) in Java

ArrayDeque.addAll(Collection<? extends E>): This method is available in java.util.ArrayDeque class of Java.

Syntax:

boolean java.util.ArrayDeque.addAll(Collection<? extends E> c)

This method takes one argument. This method adds all of the elements in the specified collection at the end of this deque.

Parameters: One parameter is required for this method.

c: the elements to be inserted into this deque.

Returns: true if this deque changed as a result of the call.

Throws:

NullPointerException - if the specified collection or any of its elements are null

Approach 1: When no exception

Java

import java.util.ArrayDeque;

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

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

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

        ArrayDeque<Integer> arrayDeque2 = new 
                         ArrayDeque<Integer>();

        arrayDeque2.add(100);
        arrayDeque2.addAll(arrayDeque);

        System.out.println(arrayDeque2.clone());

    }
}

Output:

[100, 1, 4]

Approach 2: NullPointerException

Java

import java.util.ArrayDeque;

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

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

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

        ArrayDeque<Integer> arrayDeque2 = new 
                                 ArrayDeque<Integer>();

        arrayDeque2.add(null);
        arrayDeque2.addAll(arrayDeque);

        System.out.println(arrayDeque2.clone());

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.util.ArrayDeque.addLast(ArrayDeque.java:303)
	at java.base/java.util.ArrayDeque.add(ArrayDeque.java:494)