Chapter 1 Introduction to Computers, the Internet and (Web proxy server)
Chapter 1 Introduction to Computers, the Internet and the Web 43 laborations messages that objects send to each other to communicate. The class operations that we discovered in Section 6.16 turn out to be the collaborations among the objects in our system. We determine the collaborations in our system, then collect them into a collaboration diagram the UML diagram for modeling collaborations. This diagram reveals which objects collaborate and when. We present a collaboration diagram of the people entering and exiting the elevator. Section 8.17 (Optional Case Study) Thinking About Objects: Starting to Program the Classes for the Elevator Simulation In this section, we take a break from designing the behavior of our system. We begin the implementation process to emphasize the material discussed in Chapter 8. Using the UML class diagram of Section 3.7 and the attributes and operations discussed in Sections 4.14 and 6.16, we show how to implement a class in Java from a design. We do not implement all classes because we have not completed the design process. Working from our UML diagrams, we create code for the Elevator class. Section 9.23 (Optional Case Study) Thinking About Objects: Incorporating Inheritance into the Elevator Simulation Chapter 9 begins our discussion of object-oriented programming. We consider inheritance classes sharing similar characteristics may inherit attributes and operations from a base class. In this section, we investigate how our elevator simulation can benefit from using inheritance. We document our discoveries in a class diagram that models inheritance relationships the UML refers to these relationships as generalizations. We modify the class diagram of Section 3.7 by using inheritance to group classes with similar characteristics. We continue implementing the Elevator class of Section 8.17 by incorporating inheritance. Section 10.22 (Optional Case Study) Thinking About Objects: Event Handling In this section, we include interfaces necessary for the objects in our elevator simulation to send messages to other objects. In Java, objects often communicate by sending an event a notification that some action has occurred. The object receiving the event then performs an action in response to the type of event received this is known as event handling. In Section 7.10, we outlined the message passing, or the collaborations, in our model, using a collaboration diagram. We now modify this diagram to include event handling, and, as an example, we explain in detail how doors in our simulation open upon the elevator s arrival. Section 11.10 (Optional Case Study) Thinking About Objects: Designing Interfaces with the UML In this section, we design a class diagram that models the relationships between classes and interfaces in our simulation the UML refers to these relationships as realizations. In addition, we list all operations that each interface provides to the classes. Lastly, we show how to create the Java classes that implement these interfaces. As in Section 8.17 and Section 9.23, we use class Elevator to demonstrate the implementation. Section 12.16 - (Optional Case Study) Thinking About Objects: Use Cases Chapter 12 discusses user interfaces that enable a user to interact with a program. In this section, we discuss the interaction between our elevator simulation and its user. Specifically, we investigate the scenarios that may occur between the application user and the simu Copyright 1992 2002 by Deitel & Associates, Inc. All Rights Reserved. 7/8/01
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