Java polymorphism

Question

having class Animal and a Animal subclass Cat, what is the difference between declaring Animal a = new Cat() and Cat a = new Cat()?

Answer 1

1. a is Animal and you can not use Cat methods using a.catMethod(...). But it is possible to use ((Cat)a).catMethod(...).
2. a is Cat and you can use Cat methods.

Answer 2

When using Animal a = new Cat(); a is of type Animal and you can only use public methods and public variables that class Animal has. With Cat c = new Cat(); c is a type of Cat and you can use public methods + variables of Animal + Cat.