Final Exam. Name: Student ID Number: Signature:

Transcription

1 Washington University Kenneth J. Goldman Final Exam CSE 132. Computer Science II May 7, 2007 Name: Student ID Number: Signature: Directions: This exam is closed book. You may use one 8 ½ x 11 inch page of notes (double sided), and it must be turned in with the exam. Please check that you have pages 1 through 10. Write all answers directly on the exam. Do your own work. No discussion or collaboration with other students is permitted. Sharing of materials is strictly prohibited. Any violations will result in a failing grade in the course and possibly disciplinary action. If a question is unclear to you, please walk to the front of the room and quietly ask me about it. The exam is 2 hours (1:00pm 3:00pm). Be sure to pace yourself. See suggested time allowances in the chart below. When you finish: If fewer than 10 minutes remain, please do not turn in your exam early, since getting up may disturb other students who are trying to finish. Section score possible suggested time allowances Model minutes 1:05 to 1:30 Persistence minutes 1:30 to 1:45 View minutes 1:45 to 2:00 Controllers minutes 2:00 to 2:25 Communication minutes 2:25 to 2:40 Design Review minutes 2:40 to 3:00 Total minutes Page 1

2 Part I: Application Design and Implementation (70 points) Directions: Questions in Part I build on the following general specification. Read this specification carefully and refer back to it as needed. Data Model: Washington University has hired you to develop an interactive application that simplifies degree planning for students and their advisors. Each student has a name and one or more intended degrees, all of which must be completed for the student to graduate. Each degree has a name and a set of requirements, all of which must be satisfied to complete the degree. Each course has a name and one or more prerequisite courses, all of which must be completed before that course can be taken. Each requirement has a name, and can be either a single course or a combination of other requirements. When a requirement is a combination of other requirements, it has a specified number of items that must be satisfied. For example, a combination containing three courses might specify that 2 out of 3 of the courses must be completed. Each student has a plan consisting of a List of semesters, where each semester has a name (such as Spring 2007 ) and is a Set of courses to be taken in that semester. View and Controllers: Students require the following interactive features. Browse the available degree programs and choose which one(s) to declare. See the requirements for each declared degree program. See all semesters in the plan at once, and which courses will be taken in each semester. Easily see which degree requirements are satisfied by the current plan, and which are not. Easily see, for each course in a plan, whether or not its prerequisites are satisfied. Edit the plan by adding courses to semesters in the plan, moving courses among semesters, and removing courses from the plan. (Ideally, it should be possible to add a required course directly from the degree requirements information, without having to find the course again in a separate place.) For simplicity, assume every course is taught every semester, and that there are no scheduling conflicts. You are concerned neither with editing degree requirements, nor with adding courses and their prerequisites into the system. In other words, you can assume that these things do not change. Only the student s plan changes. Page 2

3 1. Model (20 points) a. (15 points) In the following space, draw a UML diagram showing the relationships among the data model classes listed in the application specification. Show the names, parameters, and return types of the most important methods, including (1) a contains(course c) method that returns true if the given course is contained in some semester of the plan on which the method is called, and (2) an issatisfiedby(plan p) method that returns true if the plan satisfies the requirement on which the method is called. b. (5 points) Provide a complete Java implementation of the issatisfiedby method for the kind of requirement that is a combination of other requirements. Assume such requirements implement the Iterable interface. Page 3

4 2. Persistence (10 points) a. (6 points) Suppose you have decided to use the visitor pattern to traverse requirements and create a text file like the one shown. Each requirement is shown, with a star by items that are satisfied by the plan. (Assume tostring of a requirement returns its name, concatenated with (X of Y) if it is a combination requirement.) To handle indentation, you will use a modification of the visitor pattern in which the visitor is called twice for each visited object: beginvisit(x) is called when x is first visited, and endvisit(x) is called after x and all of its children have been visited. In the example shown, endvisit(core) would be called immediately after endvisit(cse332). Complete the class below, assuming the methods named in your class hierarchy exist. Computer Science (3 of 3) Core (5 of 5) CSE131* CSE132* CSE240* CSE241* CSE332 Systems (1 of 3)* CSE422 CSE425 CSE431* Electives (8 of 60) CSE public class RequirementVisitor implements BeginEndVisitor<Requirement> { PrintStream out; // a PrintStream has the methods print(string s) and println(string s) Plan plan; int indentation = 0; public RequirementVisitor(String filename, Plan p) { out = new PrintStream(new BufferedOutputStream(new FileOutputStream(filename))); plan = p; public void beginvisit(requirement req) { public void endvisit(requirement req) { b. (2 points) If you wanted to create an HTML file instead of a text file, would you still be able to use the (modified) visitor pattern? Explain. c. (2 points) Suppose you are using object serialization (the Serializable interface, etc.) to save a Plan object. Suppose each plan refers to one or more Degree objects. What could you do to prevent the Degree objects from being saved to the file? In that case, what would your application save instead, and what would it need to do when it loads a plan? Page 4

5 3. View (10 points) a. (8 points) Review the specification for the view on page 2 of this exam. In the box below, sketch the components in your user interface, as they would appear to the user. In the marigin, label each component (with an arrow) to indicate its purpose, its component type, and its layout manager. b. (2 points) Looking back at your class hierarchy, to which class(es) would you add property change support in order to allow the view to listen for updates in the model? (Just list the names of the classes below.) Page 5

6 4. Controllers (20 points) Consider a use case scenario in which the user starts the application, opens up a plan, and then: 1. The user presses the left mouse button over CSE240 in the third semester. 2. The user drags the mouse into empty space in the second semester. During the drag, the user sees the text CSE240 (as a JLabel) moving along with the mouse cursor. 3. The user releases the mouse button and sees that CSE240 has been removed from the third semester and added to the second semester. a. (12 points) Complete the implementation for the following Dragger controller to support the above use case scenario, where your GUI is displayed in the default layer of a JLayeredPane. Assume each SemesterView component has a method getsemester() that returns its Semester model object. Similarly, assume each CourseView has a getcourse() method. Finally, assume that for each CourseView object x, the Dragger object has been added as both a MouseListener and a MouseMotionListener. Recall that a component s getparent() method returns its container. public class Dragger extends MouseAdapter implements MouseMotionListener { JLayeredPane panel; JLabel feedback = new JLabel(); Semester old = null; public Dragger(JLayeredPane panel) { this.panel = panel; feedback.setvisible(false); panel.add(userfeedbacktext, JLayeredPane.DRAG_LAYER); public void mousedragged(mouseevent me) { CourseView cv = (CourseView) me.getcomponent(); Point p1 = me.getlocation(); Point p2 = SwingUtilities.convertPoint(cv, p1, panel); public void mousereleased(mouseevent me) { CourseView cv = (CourseView) me.getcomponent(); Point p = me.getlocation(); Component target = panel.getcomponentat(swingutilities.convertpoint(cv, p, panel)); public void mousemoved(mouseevent arg0) { Page 6

7 b. (2 points) Suppose that, in the above use case scenario, you wanted to provide additional feedback to the user to indicate whether or not prerequisites would (still) be satisfied if a course were dropped into the semester over which the user is dragging. How would you change the use case scenario to capture this? c. (3 points) Describe the modifications that would be necessary in the Dragger implementation to provide the user feedback you described in your answer to (b) above. d. (3 points) Suppose your initial implementation results in checking all prerequisites after every drag event, but you discover that doing this computation for each event takes too much time. How could you still provide the user feedback about prerequisites, but significantly reduce the total amount of work that would need to be done as the user drags a course object around in the panel? Page 7

8 5. Interprocess Communication (10 points) Suppose that you want to support interaction between a student and advisor as follows: 1. The advisor has an application running to accept calls, one student at a time. 2. The student places a call to the advisor. 3. The advisor s application automatically accepts the call, and the student s plan appears in the advisor s application. 4. Whenever the student does anything in the application, the event information (mouse motion, key press, etc.) is sent to the advisor s application and the Java Robot class is used to repeat the behavior at the other advisor s computer. (The advisor does not do any editing.) a. (3 points) Between sockets and RMI, which would be a better choice for implementing the communication for this application? Justify your answer. b. (3 points) Suppose that when the student and the advisor are in different cities, the mouse motion observed by the advisor is not smooth. (Sometimes motion suspends, and then resumes, in a jerky fashion.) Draw and explain a diagram to illustrate how you would solve this problem. c. (4 points) Suppose that the student and the advisor both can edit the plan, but they do not send mouse event information to each other. Instead, they perform edits on a shared model held at a server. For synchronization purposes, suppose that each semester in the shared model has an associated lock, and either the student or the advisor (but not both) holds each given lock. Suppose that to move a course in the plan from semester A to semester B, the implementation first obtains a lock on semester A, then obtains a lock on semester B, then completes the move and releases both locks. Provide a short sequence of steps by which a student and advisor could cause a deadlock. Page 8

9 Part II: Design Review (30 points) A. (10 points) Answer the following questions about a design change you made for the model (Lab 1) of the Survey application you implemented in CSE132. 1) Precisely describe the problem you encountered that prompted you to make the design change. 2) Briefly, but carefully, describe both old design, and the new design that you implemented instead. OLD DESIGN: NEW DESIGN: 3) Describe the most important problem(s) with the old design. 4) Describe the most important advantage(s) of the new design. B. (10 points) Answer the following questions about a design change you made for the controllers (Lab 4) of your Survey application. 1) Precisely describe the problem you encountered that prompted you to make the design change. 2) Briefly, but carefully, describe both old design, and the new design that you implemented instead. OLD DESIGN: NEW DESIGN: 3) Describe the most important problem(s) with the old design. 4) Describe the most important advantage(s) of the new design. Page 9

10 C. (10 points) Answer the following questions about a design change you wish you would have made for the graphical user interface view (Lab 3) of your Survey application. 1) Carefully describe the relevant aspect of your design, and the alternative you wish you had thought about at the time. YOUR DESIGN: BETTER ALTERNATIVE DESIGN (IN HINDSIGHT): 2) Explain how the alternative would have improved the user experience. 3) Explain how the alternative would have affected the software implementation. When you are finished: Check over your work. Make sure your name is on the front cover of the exam. Put your name on your 8 ½ by 11 page of notes and slip it inside the exam. If the current time is after 2:50, please remain seated until time is called. (If it is not yet 2:50, you may turn in the exam at the front of the room and leave quietly.) Enjoy your summer! Page 10