Create ArrayList from Another ArrayList in Java

This example demonstrates how to create an ArrayList from another ArrayList in Java.

Example 1: Create ArrayList from Another ArrayList in Java

To create a new ArrayList from an existing ArrayList in Java, you can use the ArrayList constructor that accepts a Collection as a parameter. 

Here's an example:
import java.util.ArrayList;
import java.util.List;

public class ArrayListExample {
    public static void main(String[] args) {
        ArrayList<String> originalList = new ArrayList<>();
        originalList.add("Element 1");
        originalList.add("Element 2");
        originalList.add("Element 3");

        ArrayList<String> newList = new ArrayList<>(originalList);

        // Print the elements of the new list
        for (String element : newList) {
            System.out.println(element);
        }
    }
}

In the code above, we create an originalList ArrayList and add some elements to it. Then, we create a new ArrayList newList by passing originalList as a parameter to the ArrayList constructor. This constructor initializes the new ArrayList with the elements of the originalList.

Finally, we iterate over the elements of the newList and print them.

Output:

Element 1
Element 2
Element 3

By using this approach, you can create a new ArrayList with the same elements as the original one. Note that the elements themselves are not copied, only references to them are stored in the new ArrayList. If you modify the elements in the originalList or newList, the changes will be reflected in both lists since they reference the same objects.

Example 2: Create ArrayList from Another ArrayList in Java

This example 2 demonstrates the following operations:
  • Create an ArrayList from another collection using the ArrayList(Collection c) constructor.
  • Adding all the elements from an existing collection to the new ArrayList using the addAll() method.
import java.util.ArrayList;
import java.util.List;

public class CreateArrayListFromCollectionExample {

    public static void main(String[] args) {
        List<Integer> firstFivePrimeNumbers = new ArrayList<>();
        firstFivePrimeNumbers.add(2);
        firstFivePrimeNumbers.add(3);
        firstFivePrimeNumbers.add(5);
        firstFivePrimeNumbers.add(7);
        firstFivePrimeNumbers.add(11);

        // Creating an ArrayList from another collection
        List<Integer> firstTenPrimeNumbers = new ArrayList<>(firstFivePrimeNumbers);


        List<Integer> nextFivePrimeNumbers = new ArrayList<>();
        nextFivePrimeNumbers.add(13);
        nextFivePrimeNumbers.add(17);
        nextFivePrimeNumbers.add(19);
        nextFivePrimeNumbers.add(23);
        nextFivePrimeNumbers.add(29);

        // Adding an entire collection to an ArrayList
        firstTenPrimeNumbers.addAll(nextFivePrimeNumbers);

        System.out.println(firstTenPrimeNumbers);
    }
}

Output

[2, 3, 5, 7, 11, 13, 17, 19, 23, 29]

Reference


Java ArrayList Source Code Examples