The output -although you could have tried it yourself for practicing ;)- is the value of the variable 'i'.
Why? Because it is the whole point of polymorphism.
Although your reference's type is MySuper, the actual object being referenced is a MySub.
You have the method disp() in the MySuper superclass, this allows you to call that method, because the JVM knows there is such a method,
because the MySuper type reference obj tells it to it.
But since your object is of MySub type, calling the disp() method on it will invoke the MySub.disp() method.
This is because MySub only knows about its own method, because it overrid it.
(Except if inside the class, then you could invoke the superclass' method by super.disp() )