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Java ArrayList addall() Method with Example

Last Updated : 10 Dec, 2024

The addAll() method in the ArrayList class is used to add all the elements from a specified collection into an ArrayList. This method is especially useful for combining collections or inserting multiple elements at once.

Example: Here, we will add elements to the end of the list.

// Java program to demonstrate 
// adding all elements to the end of a list
import java.util.ArrayList;
public class GFG {
  
    public static void main(String[] args) {
      
        // Creating an ArrayList and 
        // adding initial elements
        ArrayList<String> l1 = new ArrayList<>();
        l1.add("Java");
        l1.add("C++");

        // Creating another ArrayList 
        // with elements to be added
        ArrayList<String> l2 = new ArrayList<>();
        l2.add("C");

        // Adding all elements 
        // from l2 to l1
        l1.addAll(l2);
        System.out.println("" + l1);
    }
}

Now, there are two versions of the ArrayList addAll() method, i.e., one that appends elements at the end of the list and another that inserts elements at a specified position in the list.

This version appends all elements of the specified collection to the end of the ArrayList.

Syntax:

boolean addAll(Collection c)

• Parameters: c: The collection containing elements to be added to the ArrayList.
• Return Value: true: If the elements were successfully added.

Implementation:

// Java program to demonstrate 
// adding all elements at the end of ArrayList
import java.util.ArrayList;

public class GFG {
    public static void main(String[] args) {
      
        ArrayList<Integer> l1 = new ArrayList<>();
        l1.add(10);
        l1.add(20);

        ArrayList<Integer> l2 = new ArrayList<>();
        l2.add(30);
        l2.add(40);

        // Adding all elements from 
        // l2 to l1
        l1.addAll(l2);

        System.out.println("Final ArrayList: " + l1);
    }
}

Final ArrayList: [10, 20, 30, 40]

This version inserts all elements from the specified collection into the ArrayList at the specified index. It shifts the current elements and subsequent elements to the right.

Syntax:

boolean addAll(int index, Collection c)

Parameters:

• index: The position at which the elements should be inserted.
• c: The collection containing elements to be added.

// Java program to demonstrate adding 
// elements at a specific index
import java.util.ArrayList;

public class GFG {
  
    public static void main(String[] args) {
      
        ArrayList<String> l1 = new ArrayList<>();
        l1.add("Java");
        l1.add("C++");
        l1.add("Python");

        ArrayList<String> l2 = new ArrayList<>();
        l2.add("C");
        l2.add("AI");

        // Adding elements of 
        // l2 at index 2
        l1.addAll(2, l2);

        System.out.println("" + l1);
    }
}

[Java, C++, C, AI, Python]

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