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 11 folder of the code download. It is called Inheritance Example.
Create a new project called Inheritance Example using the Empty Activity template and then add three new classes in the usual way. Name one AlienShip, another Fighter, and the last one Bomber.
Here 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 logcat so that we can see when it is being used. The AlienShip class also has a new method, fireWeapon, which is declared abstract.
Declaring a class as abstract guarantees that any class that are subclasses of AlienShip must implement their own version of fireWeapon...