Collections.addAll(Collection, E...) in Java

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

Syntax:

<E> boolean java.util.Collections.addAll(Collection<? super E> c, E... elements)

This method adds all of the specified element to the specified collection. Elements to be added may be specified individually or as an array.

Parameters:

c: the collection into which elements are to be inserted.

elements: the elements to insert into c.

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

Throws:

1. UnsupportedOperationException - if c does not support the add operation.

2. NullPointerException - if elements contain one or more null values and c does not permit null elements, or if c or elements are null.

3. IllegalArgumentException - if some property of a value in elements prevents it from being added to c.

Approach 1: When no exception

Java

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

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

        List<Integer> arrlist = new ArrayList<Integer>();

        Collections.addAll(arrlist, 1, 3, 4);

        System.out.println(arrlist);

    }
}

Output:

[1, 3, 4]

Approach 2: NullPointerException

Java

import java.util.Collections;
import java.util.List;

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

        List<Integer> arrlist = null;

        Collections.addAll(arrlist, 1, 3, 4);

        System.out.println(arrlist);

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.Collection.add(Object)" because "c" is null
	at java.base/java.util.Collections.addAll(Collections.java:5593)