About Question enthuware.ocajp.i.v7.2.1131 :

[ETS User]

I cannot conceptually get how we can have a static reference to a class of the type that it's being defined in. I get the concept of the question but not how 'static TestClass ref;' works.

Can you explain please?
Thanks

[admin]

In this case, ref is just a static field in class, which happens to be of type TestClass.

I am just guessing that you are confused because at the time of declaring the class, you dont know the size of the class and so having a member of the same time may cause a recursion type scenario.

But ref is just like a pointer. So it doesn't have to know the space needed to store an object of type TestClass because the size of the pointer is constant. So it can point to any object even if that object is of the same type as the declaring class and even if the type of the object that it is pointing to is not known.

HTH

[Guest]

So if you did
static TestClass ref = new TestClass();

would it be an error?

[admin]

No, why? As I said, ref is just a pointer. It can point to anything and its size would still be the same.

[admin]

As an exercise, try running this code:

Code: Select all

public class RecursiveObject {
    public RecursiveObject obj = new RecursiveObject(); //Make it static and try again
    int[] ia = new int[1000];
    public static void main(String[] args) {
        RecursiveObject ro = new RecursiveObject();
    }
}

[ncowan]

Thanks for the utterly useless explanation of "non sense!", really helped me out.

[admin]

Not sure what explanation would one need here. The statement is simply not true. Anyway, it has been updated to make it more clear.

thank you for your feedback!