Java : Class inheriting self

Question

I know this is pointless: I just find it funny and I want to inquire more about the mechanics of what happens when you create a class that inherits itself, resulting in a stack

Answer 1

The example you posted could get problematic if we change it a bit more:

public class Outside {

    public class Inside extends Outside {

            public Inside(int val) {
        }

    }

    private Inside i;

    public Outside() {
        i = new Inside();
    }
}

But this is not really related to the fact that Inside is an inner class of Outside, it could have happened with separate top-level-classes identically.

Answer 2

Extending oneself generates an error of cyclic inheritance (which java doesn't allow). Your code sample does compile and is valid.

---

Due to Vladimir Ivanov's persistence, I will fix my edit.

Your code throws a StackOverflowError because of the following.

Inside o = new Inside(0);

Since Inside extends Outside, Inside first calls the super() method implicitly (since you've not called it yourself). Outside() constructor initializes Inside o and the cycle runs again, until the stack is full and it overflow (there's too many Inside and Outside inside the heap stack).

Hope this helps especially Vladimir Ivanov.