List addAll() Method in Java with Examples

This method appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection’s iterator.

Syntax:

boolean addAll(Collection c)

Parameters: This function has a single parameter, i.e, Collection c, whose elements are to be appended to the list.

Returns: It returns true if the elements of specified list is appended and list changes.

Below programs show the implementation of this method.

Program 1:

// Java code to show the implementation of
// addAll method in list interface
import java.util.*;
public class GfG {

    // Driver code
    public static void main(String[] args)
    {

        // Initializing a list of type arraylist
        List<Integer> l = new ArrayList<>();
        l.add(10);
        l.add(15);
        l.add(20);
        System.out.println(l);

        // Initializing a collection to be appended to list
        ArrayList<Integer> arr = new ArrayList<Integer>();
        arr.add(100);
        arr.add(200);
        arr.add(300);
        System.out.println(arr);

        l.addAll(arr);

        System.out.println(l);
    }
}

Output:

[10, 15, 20]
[100, 200, 300]
[10, 15, 20, 100, 200, 300]

Program 2: Below is the code to show implementation of list.addAll() using Linkedlist.

// Java code to show the implementation of
// addAll method in list interface
import java.util.*;
public class GfG {

    // Driver code
    public static void main(String[] args)
    {

        // Initializing a list of type Linkedlist
        List<Integer> l = new LinkedList<>();
        l.add(10);
        l.add(15);
        l.add(20);
        System.out.println(l);

        // Initializing a collection to be appended to list
        ArrayList<Integer> arr = new ArrayList<Integer>();
        arr.add(100);
        arr.add(200);
        arr.add(300);
        System.out.println(arr);

        l.addAll(arr);

        System.out.println(l);
    }
}

Output:

[10, 15, 20]
[100, 200, 300]
[10, 15, 20, 100, 200, 300]

Reference:
Oracle Docs