Question

I have a weird Java question:

As we know:

1. All Java classes extend java.lang.Object
2. All Java classes cannot extend itself

Then, java.lang.Object must extend java.lang.Object, which is itself, therefore, it should be impossible. How is Object implemented in Java?

Answer 1

Object is an exception to the first rule, and has no superclass. From JLS3 8.1.4:

The extends clause must not appear in the definition of the class Object, because it is the primordial class and has no direct superclass.

You can also try it out with reflection:

Object.class.getSuperclass(); // returns null