Android How to Program, 3/e

G.2 Superclasses and Subclasses

Often, an object of one class is an object of another class as well. Figure G.1 lists several examples of superclasses and subclasses—superclasses tend to be “more general” and subclasses “more specific.” For example, a CarLoan is a Loan as are HomeImprovementLoans and MortgageLoans. Thus, in Java, class CarLoan can be said to inherit from class Loan. In this context, class Loan is a superclass and class CarLoan is a subclass. A CarLoan is a specific type of Loan, but it’s incorrect to claim that every Loan is a CarLoan—the Loan could be any type of loan.

Fig. G.1 Inheritance examples

Superclass	Subclasses
Student	GraduateStudent, UndergraduateStudent
Shape	Circle, Triangle, Rectangle, Sphere, Cube