When you are considering using inheritance, ask yourself whether the subclass really is a more specialized version of the superclass. In this case, a car is a type of vehicle, so the inheritance ...

Java’s interface ... multiple implementation inheritance, and the root of all classes. In addition, I have introduced the specialized topics of enumerated types and singletons.

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 ...