Java特性复习.pptVIP

* 类的设计 Fig. 3-3 The files for an interface, a class that implements the interface, and the client. * 类的设计 An Interface as a Data Type An interface can be used as a data type or … * 类的设计 Generic Types Within an Interface Recall class OrderedPair from Chapter 2 Note the setPair method Consider an interface Pairable that declares this method  A class that implements this interface could begin with the statement * 类的设计 The Interface Comparable Method compareTo compares two objects, say x and y Returns signed integer Returns negative if x y Returns zero if x == y Returns positive if x y * 类的设计 Consider a class Circle Methods equals, compareTo Methods from Measurable View source code Note Implements Measurable interface Shown with two alternative versions of compareTo * 类的设计 Extending an Interface Use inheritance to derive an interface from another When an interface extends another It has all the methods of the inherited interface Also include some new methods Also possible to combine several interfaces into a new interface Not possible with classes * 类的设计 Interfaces Versus Abstract Classes Purpose of interface similar to purpose of abstract class But … an interface is not a base class It is not a class of any kind Use an abstract base class when You need a method or private data field that classes will have in common Otherwise use an interfac * 类的设计 Named Constants Within an Interface An interface can contain named constants Public data fields initialized and declared as final Consider an interface with a collection of named constants Then derive variety of interfaces that can make use of these constants * 类的设计 Choosing Classes Look at a prospective system from a functional point of view Ask What or who will use the system What can each actor do with the system Which scenarios involve common goals Use a case diagram * 类的设计 Fig. 3-4 A use case diagram for a registration system * 类的设计 Identifying Classes Describe the system Identify nouns and verbs N