java - Casting subclasses extending the same original class -

How can I grow two in Java?

  extends class B object {} class extends C object {} bb = new b (); C = (c) b; // can not be inserted from B to C  

You can not do Rename a little name:

  Enhances square Ford's chevrolet car {} Ford Ford = New Ford (); Chevrolet Chevrolet = (Chevrolet) Ford;  

Both are cars, so you can say

  car car = Ford;  

But no more than that.