Question

I have a class Super and several subclases Sub1, Sub2,…

Is there a way to instantiate objects sub1, sub2 that would share the same super instance?

The situation comes from an inner nested class configuration like this:

Super{  
    superFields...
    Sub1{...}
    Sub2{...}
    ........
    }

But the inner claeses have grown too much, and I woud feel more confortable having them in separate files. They need to share the same instance of superFields, so my question.

Answer 1

Inner classes are implemented by having the superclass as argument of all their constructors.

So that’s what you can do as well:

public class Sub1 {
   private Superclass superclass;
   public Sub1(Superclass superclass) {
       this.superclass = superclass;
   }
}

and whenever you want to instantiate the subclass from within the superclass:

Sub1 sub = new Sub1(this);