How to create Immutable List in java?

Question

I need to convert mutable list object to immutable list. What is the possible way in java?

public void action() {
    List mutableList =          


        

Answer 1

Below solution is for making list as Immutable without using any API.

Immutable Object with ArrayList member variable

public final class Demo {

    private final List list = new ArrayList();

    public Demo() {
        list.add("A");
        list.add("B");
    }

    public List getImmutableList() {
        List finalList = new ArrayList();
        list.forEach(s -> finalList.add(s));
        return finalList;
    }

    public static void main(String[] args) {
        Demo obj = new Demo();
        System.out.println(obj.getImmutableList());
        obj.getImmutableList().add("C");
        System.out.println(obj.getImmutableList());
    }
}

So the actual list will not change, always output will be [A,B]