Compare inheritance and composition, the two fundamental ways to relate Java classes, then practice debugging ClassCastExceptions in Java inheritance.

Get started with polymorphism in Java and how to do method invocation in polymorphic method calls.

A method might accept a specific type and its subclasses, but you want to restrict usage to a select few implementations of your own design. Java's open inheritance model can feel like an open ...

This looks like the Liskov substitution principle that Uncle Bob Martin described: Substitute a derived class (Square) for a base class (Rectangle). From the standpoint of the compiler, the above code ...