DownCasting

Question

Hello... Please I'm a little bit confused by this statement:
"But if you have a group of different Animals and want to downcast them all to a Cat, then there's a chance that some of these Animals are actually Dogs, so the process fails."

Does it mean that, if we have for instance,
Animal b = new Dog();

And doing this;
((Cat)b).makeSound();

will fail?

Answer 1

Yes it will fail.

Think of it this way.

You are assigning the value, 'Dog' to the variable Animal. This is allowed, since a Dog is an Animal.

Then, you cast the variable to a Cat.
But it still has the value of Dog!!

A Cat is a Dog?! This is madness! Error!

That's why you may see things like this:

if(myAnimal instanceof Dog)
((Dog)myAnimal).makeSound();
else if(myAnimal instanceof Cat)
((Cat)myAnimal).makeSound();