【文章內(nèi)容簡介】 ide invaluable information to help navigate through the iterations of the design Gilbert and McCarty in ObjectOriented Design in Java aptly point out,“ to a system user, the user interface is the system.”There are several ways to create a user interface can sketch the user interface by simply drawing it on paper or a can use a special prototyping tool or even a language environment like Visual Basic, which is often used for rapid prototyping. Or you can use the IDE from your favorite development tool to create the prototype. However you develop the user interface prototype, make sure that the users have the final say on the look and feel. 4 Inheritance One of the most powerful features of OO programming is, perhaps, code reuse. Structured design provides code reuse to a certain extent— you can write a procedure and then use it as many times as you want. However, OO design goes an important step further, allowing you to define relationships between classes that facilitate not only code reuse, but also better overall design, by anizing classes and factoring in monalties of various classes. Inheritance is a primary means of providing this functionality. Inheritance allows a class to inherit the attributes and methods of another allows creation of brand new classes by abstracting out mon attributes and behaviors. One of the major design issues in OO programming is to factor out monality of the various classes. 5 Using Object Persistence Object persistence is another issue that must be addressed in many OO systems. Persistence is the concept of maintaining the state of an you run a program, if you don’ t save the object in some manner, the object simply dies, never to be transient objects might work in some applications, but in most business systems, the state of the object must be saved for later use. In its simplest form, an object can persist by being serialized and written to a flat stateoftheart technology is now it is true that an object theoretically can persist in memory as long as it is not destroyed,we will concentrate on storing persistent objects on some sort of storage are three primary storage devices to consider: . Flat file system— You can store an object in a flat file by serializing the has very limited use. . Relational database— Some sort of middleware is necessary to convert an object to a relational model. .OO database— This is the logical way to make objects persistent, but most panies have all their data in legacy systems and are just starting to explore object databases. Even brandnew OO applications must usually interface with legacy data. 6 What Is UML? UML, as its name implies, is a modeling UML User Guide defines UML as “ a graphical language for visualizing, specifying, constructing and documenting the artifacts of a softwareintensive system.” UML gives you a standard way to write the system’ s blueprints. In a nutshell,UML offers a way to graphically represent and