Without inheritance, classes would simply be data structures with associated behaviors. That alone would be a powerful improvement over procedural languages, but inheritance adds an entirely new dimension. Through inheritance, you can build new classes based on existing ones. In this way, your classes become reusable and extensible components. This chapter will teach you the different ways to leverage the power of inheritance. You will learn about the specific syntax of inheritance as well as sophisticated techniques for making the most of inheritance.
After finishing this chapter, you will understand:
How to extend a class through inheritance
How to employ inheritance to reuse code
How to build interactions between superclasses and subclasses
How to use inheritance to achieve polymorphism
How to work with multiple inheritance
How to deal with unusual problems in inheritance
The portion of this chapter relating to polymorphism draws heavily on the spreadsheet example discussed in Chapters 8 and 9. If you have not read Chapters 8 and 9, you may wish to skim the sample code in those chapters to get a background on this example. This chapter also refers to the object-oriented methodologies described in Chapter 3. If you have not read that chapter and are unfamiliar with the theories behind inheritance, you should review Chapter 3 before continuing.
In Chapter 3, you learned that an "is-a" relationship recognizes ...