In Java, what does 'this' indicate in a superclass method called on a subclass that inherits that method?

Polymorphism & Overloading

Polymorphism

1. Polymorphism is exhibited when a reference.method() is invoked
2. This is by nature a dynamic behavior based on the actual object type referenced by the reference
3. This is where the lookup tables(like vmt in c++) comes into play
4. Depending on the object pointed by the reference, runtime will decide on the actual method to invoke

Overloading

1. Method overloading in a compile time decision
2. The signature of the method is fixed at compile time
3. There is no runtime lookup needed for any polymorphism exhibited based on the method's parameter types
4. The parameter is just a parameter for the method in context and it does not care about the polymorphism exhibited by the type

What is happening in the current example?

    static class Lecture {
        public void addAttendant(Person p) {
            p.join(this);
        }
    }

1. Assuming there is a child class of Lecture overriding addAttendant, then polymorphism can control which method will be called based on the object type when someone invokes a method on a reference type of Lecture or one of its subclass(es).
2. But, for any call that will eventually land on the Lecture.addAttendant, the method signature that matches the p.join(this) is join(Lecture)(even though p could be dynamically referenced). Here there is no polymorphism even though the object referenced by this could be a polymorphic type.