Java™ How To Program (Early Objects), Tenth Edition

Motivating static

Let’s motivate static data with an example. Suppose that we have a video game with Martians and other space creatures. Each Martian tends to be brave and willing to attack other space creatures when the Martian is aware that at least four other Martians are present. If fewer than five Martians are present, each of them becomes cowardly. Thus, each Martian needs to know the martianCount. We could endow class Martian with martianCount as an instance variable. If we do this, then every Martian will have a separate copy of the instance variable, and every time we create a new Martian, we’ll have to update the instance variable martianCount in every Martian object. This wastes space with the redundant copies, wastes time in updating ...