ArrayList.addAll() index in Java

ArrayList.addAll(): This method is available in java.util.ArrayList class of Java.

Syntax:

boolean java.util.ArrayList.addAll(int index, Collection<? extends Integer> c)

This method takes two arguments as its parameters. This method inserts all of the elements in the specified collection into this list, starting at the specified position.

Parameters: Two parameters are required for this method.

index: index at which to insert the first element from the specified collection.

c: a collection containing elements to be added to this list.

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

Throws:

1. IndexOutOfBoundsException - if the index is out of range(index < 0 || index > size()).

2. NullPointerException - if the specified collection is null

Approach 1: When no exceptions

Java

import java.util.ArrayList;

public class ArrayListAddAllAtIndex {
    public static void main(String[] args) {
        ArrayList<Integer> arr = new ArrayList<>();
        ArrayList<Integer> arr1 = new ArrayList<Integer>();
        arr1.add(1);
        arr1.add(2);
        // Add all in arr
        arr.add(5);
        arr.add(4);
        arr.add(6);
        arr.addAll(1, arr1);

        arr.forEach((n -> System.out.print(n + " ")));

    }
}

Output:

5 1 2 4 6 

Approach 2: IndexOutOfBoundsException

Java

import java.util.ArrayList;

public class ArrayListAddAllAtIndex {
    public static void main(String[] args) {
        ArrayList<Integer> arr = new ArrayList<>();
        ArrayList<Integer> arr1 = new ArrayList<Integer>();
        arr1.add(1);
        arr1.add(2);
        // Add all in arr
        arr.add(5);
        arr.add(4);
        arr.add(6);
        arr.addAll(8, arr1);

        arr.forEach((n -> System.out.print(n + " ")));

    }
}

Output:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 8, Size: 3
	at java.base/java.util.ArrayList.rangeCheckForAdd(ArrayList.java:756)
	at java.base/java.util.ArrayList.addAll(ArrayList.java:700)

Approach 3: NullPointerException 

Java

import java.util.ArrayList;

public class ArrayListAddAllAtIndex {
    public static void main(String[] args) {
        ArrayList<Integer> arr = new ArrayList<>();
        ArrayList<Integer> arr1 = null;
        // Add all in arr
        arr.add(5);
        arr.add(4);
        arr.add(6);
        arr.addAll(1, arr1);

        arr.forEach((n -> System.out.print(n + " ")));

    }
}

Output:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.util.Collection.toArray()" because "c" is null
	at java.base/java.util.ArrayList.addAll(ArrayList.java:702)
	at com.example.ArrayList.ArrayListAddAllAtIndex.main(ArrayListAddAllAtIndex.java:13)