Implement a final class without the “final” keyword

Question

A friend of mine was asked that question in his on-phone job interview a couple of days a go. I don\'t have a clue. can anyone suggest a solution? (His job interview is ov

Answer 1

You can make your class immutable without using final keyword as:

1. Make instance variable as private.
2. Make constructor private.
3. Create a factory method which will return the instance of this class.

I am providing immutable class here in Java.

class Immutable {
    private int i;
    private Immutable(int i){
     this.i = i;
    }
    public static Immutable createInstance(int i){
         return new Immutable(i);
    }
    public int getI(){return i;}
}
 class Main {
    public static void main(string args[]){
       Immutable obj = Immutable.createInstance(5);
    }
}