Why Downcasting throws Exception?

Question

In java:

Base b = new Base();
Derived d = (Derived)b; 

throws ClassCastException. Why? Why downcasting throws Exception<

Answer 1

You cannot cast a derived class as the base class. You may assign b as either a Base or a Derived, but you may only assign d as a Derived. Long story short, you may only assign a variable declared as Base a value that is of the same type (Base) or a derived type.

This is okay (I'm just using new as an example, what matters is the data types):

Base b = new Base();
Base b = new Derived();
Derived d = new Derived();

But this is not:

Derived d = new Base();

This is the way that inheritance works