Head First Java, 2nd Edition

Chapter 7. Inheritance and Polymorphism: Better Living in Objectville

Plan your programs with the future in mind. If there were a way to write Java code such that you could take more vacations, how much would it be worth to you? What if you could write code that someone else could extend, easily? And if you could write code that was flexible, for those pesky last-minute spec changes, would that be something you’re interested in? Then this is your lucky day. For just three easy payments of 60 minutes time, you can have all this. When you get on the Polymorphism Plan, you’ll learn the 5 steps to better class design, the 3 tricks to polymorphism, the 8 ways to make flexible code, and if you act now—a bonus lesson on the 4 tips for exploiting inheritance. Don’t delay, an offer this good will give you the design freedom and programming flexibility you deserve. It’s quick, it’s easy, and it’s available now. Start today, and we’ll throw in an extra level of abstraction!

Chair Wars Revisited...

Remember way back in Chapter 2, when Larry (procedural guy) and Brad (OO guy) were vying for the Aeron chair? Let’s look at a few pieces of that story to review the basics of inheritance.

LARRY: You’ve got duplicated code! The rotate procedure is in all four Shape things. It’s a stupid design. You have to maintain four different rotate “methods”. How can that ever be good?

BRAD: Oh, I guess you didn’t ...