The inheritance mini app

We have looked at the way we can create hierarchies of classes to model the system that fits our app. So, let's try out some simple code that uses inheritance. The completed code is in the Chapter 9 folder of the code download. It is called Inheritance Example.

Create three new classes in the usual way. Name one AlienShip, another Fighter, and the last one Bomber.

The following is the code for the AlienShip class. It is very similar to our previous class demo, AlienShip. The differences are that the constructor now takes an int parameter, which it uses to set the shield strength.

The constructor also outputs a message to the console, so we can see when it is being used. Additionally, the AlienShip class has a new method, fireWeapon, that is declared abstract. This guarantees that any class that subclasses AlienShip must implement its own version of fireWeapon. Notice the class has the abstract keyword as part of its declaration. We have to do this because one of its...