Android™ How to Program, Second Edition

G.12.2. Interface Payable

The declaration of interface Payable begins in Fig. G.23 at line 4. Interface Payable contains public abstract method getPaymentAmount (line 6). The method is not explicitly declared public or abstract. Interface methods are always public and abstract, so they do not need to be declared as such. Interface Payable has only one method—interfaces can have any number of methods. In addition, method getPaymentAmount has no parameters, but interface methods can have parameters. Interfaces may also contain fields that are implicitly final and static.

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 1      // Fig. G.23: Payable.java 2      // Payable interface declaration. 3  4      public interface Payable                                              ...