October 2001
Intermediate to advanced
640 pages
18h 58m
English
Content preview from An Introduction to Object-Oriented Programming, 3rd Edition
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Chapter 10
Subclasses and Subtypes
There is a paradox that lies at the heart of the way inheritance and substitution are used in statically typed object-oriented languages. This paradox derives from the twin concepts of subclass and subtype. In this chapter we will explore these concepts and this paradox.
To say that one class is a subclass of another is to simply assert that it has been built using inheritance. The new class is declared using an existing class as a basis, as in the following Java class declaration.
class Child extends Parent {
... // class definition
}
The point is that the subclass relationship is asserting a statement about definition, about how the new class was constructed. It says nothing ...
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