oop « subclass « Java Class Q&A

1. How can I force subclasses to redefine a constant in Java?    stackoverflow.com

How can I have a generic abstract class, let's say Animal, and have it implement a constant (or a variable; it doesn't mind) which must be redefined by all subclasses? Example:

abstract class ...

2. How do I define a constructor for all subclasses    stackoverflow.com

I'm making a chess game and each Piece has a subclass - King, Queen, Rook etc Each Piece has a playerId attribute which I want to set like this:

public abstract class Piece ...

3. What is a Subclass    stackoverflow.com

What is a "subclass" in java? I know about classes and methods, but I do not know about subclasses. I will be more than happy to have a good explanation. Thanks!

4. Is there a way of retrieving the type of a subclass, when an object is passed in as type super class?    stackoverflow.com

If I had a method signature

public void myMethod(SuperClass s){
}