In this example, we will see how to create an immutable ArrayList using Collections.unmodifiableList() method with an example.

Create Immutable ArrayList with Collections.unmodifiableList() Exmaple

public class ImmutableListExample {

    public static void main(String[] args) {

        // Creating an ArrayList of String using
        List < String > fruits = new ArrayList < > ();
        // Adding new elements to the ArrayList
        fruits.add("Banana");
        fruits.add("Apple");
        fruits.add("mango");
        fruits.add("orange");

        fruits = Collections.unmodifiableList(fruits);

        // Creating Immutable List
        //fruits.add("Strawberry"); // Exception in thread "main"
        // java.lang.UnsupportedOperationException<String> fruits = List.of("Banana", "Apple", "Mango", "Orange");
        fruits.forEach(e - > System.out.println(e));
    }
}

Output:

Banana
Apple
mango
orange

References

• https://www.javaguides.net/2019/12/java-9-listof-method-create-immutable.html