.addAll()

The .addAll() method is used to add the contents of a collection to an instance of the ArrayList class.

Syntax

arrayListInstance.addAll(index, collection);

The contents of collection are inserted into the arrayListInstance at the specified index. The collection must be of the same data type as arrayListInstance.

Example

The following example creates two ArrayLists and inserts one into the other.

import java.util.ArrayList;
public class testAddAll {
public static void main(String[] args) {
// Create first ArrayList
ArrayList<String> list1 = new ArrayList<String>();
// Add items to first ArrayList
list1.add("A");
list1.add("B");
list1.add("C");
list1.add("D");
// Create second ArrayList
ArrayList<String> list2 = new ArrayList<String>();
// Add items to second ArrayList
list2.add("W");
list2.add("X");
list2.add("Y");
list2.add("Z");
// Print first ArrayList
System.out.println("List 1:");
System.out.println(list1);
// Print second ArrayList
System.out.println("List 2:");
System.out.println(list2);
// Add second ArrayList to first ArrayList at index 3
list1.addAll(3, list2);
// Print the combined ArrayList
System.out.println("List 1 + List 2:");
System.out.println(list1);
}
}

The output would look like this:

List 1:
[A, B, C, D]
List 2:
[W, X, Y, Z]
List 1 + List 2:
[A, B, C, W, X, Y, Z, D]

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