Inheritance and the “this” keyword

Question

Suppose that we have next situation:

Parent class A:

class A{  
    public A(){}
    public doSomething(){  
        System.out.println(this.getCla         


        

Answer 1

Think of it in terms of runtime vs static types:

Animal a = new Cat();

The static type (in this case written on the left hand side) of variable a is Animal (you couldn't pass a into a method that required a Cat without a downcast) but the runtime type of the object pointed to by a is Cat.

a.getClass() exposes the runtime type (if it helps think of it as the most specific subtype).

Interestingly in Java overloaded methods are resolved at compile-time (without looking at the runtime type). So given then following two methods:

foo(Cat c);
foo(Animal animal)

Calling foo(a) would call the latter. To 'fix' this the visitor pattern can be used to dispatch based on the runtime type (double dispatch).