C Sc 335 Practice Test 2 Answers 1a) Create an initial list of classes that would do a good job of modeling this system (ANSWER MAY VARY)

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1 C Sc 335 Practice Test 2 Answers 1a) Create an initial list of classes that would do a good job of modeling this system (ANSWER MAY VARY) Candidate Class Name Single Responsibility Customer (or Rentor) Stores all needed info about any rentor such as name, phone number, credit card number, list of rentals, history,... Cashier Gather all data needed to make and record one transaction. A Cashier also produces a receipt (the transaction report with "typical" information) Video Store all necessary data about a physical rental: Customer, UPC, Title, cost to rent... VideoCollection A list of all video titles that can be borrowed (only one record for dozens of copies) Transaction Store all needed data for each rental such as borrower, unique video identifier more possible such as TransactionLog Maintain a list of all transactions 1b) Write a sequence diagram to represent the objects involved in a use case that begins when a customer arrives at a checkout with videos to rent. (YOUR ANSWER MAY VARY) Here's another example of a sequence diagram drawn with a tool from an anonymous source (different class names, but more readable perhaps) Clerk VideoStore VideoCollection Video VideoRental Transaction Report rent(barcode) Top Package::Customer get(barcode) find(barcode) getbarcode() gotvideo addrental PrintTicket 1

2 2. Pattern Name Synopsis a. Iterator Provide a way to access the elements of a collection sequentially without revealing the underlying implementation. b. TBA TBA c. TBA TBA 3. Known design pattern: Composite, 3A) UML diagram. Note: The practice test had an inferior general form of the Composite Design Pattern, if on the test, we ll use this general form (from WikiPedia): 3A) Draw the UML diagram 3B) class Abstract public abstract class Abstract { private String name; public Abstract(String name) { this.name = name; public String getname() { return name; abstract public void display(string prepend); 2

3 3C) The Primitive and Composite classes public class Primitive extends Abstract { public Primitive(String name) { super(name); public void add(primitive primitive) { System.out.println("'Cannot add to a PrimitiveElement'"); public void display(string prepend) { System.out.println(prepend + "draw " + getname()); class Composite extends Abstract { private ArrayList<Abstract> elements = new ArrayList<Abstract>(); public static final String INDENT = " "; public Composite(String name) { super(name); public void add(abstract a) { elements.add(a); public void display() { public void display(string prepend) { System.out.println(prepend + "draw " + getname()); // display each child element in this Composite Iterator itr = elements.iterator(); while (itr.hasnext()) { Abstract a = (Abstract) itr.next(); a.display(prepend + INDENT); 4. Write code, interfaces and/or classes for a problem using a Design Pattern not previously discussed in class or section. One of these: Adapter, Proxy, Mediator, State, or Chain of Responsibility. Question not given for obvious reasons. It would look like the one above. There may only be one Design Pattern Question on the test if Rick thinks it would be too much 5. This server now awaits one client Client wrote: I am client Server wrote: This server is shutting down. 6. I really think a similar question on the real test will be shorter, it has to be. But still think about paintcomponent, draw, a few geom classes, and a timer public class HangmanPanel extends JPanel implements Observer { private int wrongs; public HangmanPanel() { wrongs = 0; 3

4 @Override public void paintcomponent(graphics g) { super.paintcomponent(g); Graphics2D g2 = (Graphics2D) g; // Always draw the gallows and the noose at startup g2.fill(new Rectangle2D.Double(5, 230, 200, 5)); // base of scaffold g2.fill(new Rectangle2D.Double(5, 10, 5, 225)); // side of scaffold g2.fill(new Rectangle2D.Double(5, 5, 80, 5)); // top of scaffold g2.draw(new Line2D.Double(new Point(80, 10), new Point(80, 30))); // noose if (wrongs > 0) g2.draw(new Ellipse2D.Double(70, 30, 20, 20)); if (wrongs > 1) g2.draw(new Line2D.Double(80, 51, 80, 110)); if (wrongs > 2) g2.draw(new Line2D.Double(80, 70, 50, 90)); if (wrongs > 3) g2.draw(new Line2D.Double(80, 70, 110, 90)); if (wrongs > 4) g2.draw(new Line2D.Double(80, 110, 60, 140)); if (wrongs > 5) g2.draw(new Line2D.Double(80, 110, 100, 140)); // x, y values could be very rough public void update(observable hangmangame, Object ignored) { // Still need to remember MVC wrongs = ((HangmanModel) hangmangame).numberofwrongguesses(); repaint(); 7. Agile/Scrum Software Practices (10pts) In Scrum, should a team know all tasks needed for a sprint by the end of the planning meeting B Maybe, about 60% of the tasks are like to be identified In Scrum, what is the longest allowable duration <a, b, or c>? (1pt) C One month In Scrum, it is acceptable to postpone testing until the next sprint <true or false>? FALSE How can one Scrum team build a potentially shippable product increment within one sprint? Circle all letters that apply A B and C a. By using modern software engineering approaches such as TDD, continuous design, and continuous integration b. By checking in code several times a day and reducing or eliminating branches in GIT c. By improved collaboration techniques such as pair programming and having the team all work in the same room d. This cannot be done What s a better measure of progress, how much work has been <started or finished>? FINISHED_ A product backlog is more about the what and the tasks are more about the how <true or false> TRUE List the correct order of things to do in an Agile Lifecycle: 3) Update progress during an iteration 2) Plan an iteration / sprint 1) Create a product backlog of user stories C, then B, then A 4

5 Does a story point of 8 predict 8 hours of actual work <yes or no>? NO Does a task estimate of 8 predict 8 hours of actual work <yes or no>? YES 8. Check the correct answer with an X, 0.5 pts each a. All Java keywords are written in lower case. _X_true false b. Does a call to System.gc() force garbage collection to take place? yes always _x_ not always c. Assume: byte a = 3; byte b = 2; byte c; What is the result of c = a + b; X compile time error Type mismatch: cannot convert from int to byte c == 5 c == 3 runtime exception 9. Choose the better design and explain why... 1) b When a method name does not reveal its purpose, change the name of the method. Use the refactoring Rename Method to change empty to isempty (unless empty does really empty the container). BTW: The C++ STL has many collection classes (stack, queue, list) where empty does not mean empty, it returns true if the stack isempty. Also, pop can modify and return as long as it is documented. You could argue that pop should only modify, and some people do. 2) b Whenever there is a public field, make it private and provide accessors. This prevents other object from modifying a field, which would be the worst form of coupling. Use the "Encapsulate Field" refactoring (Eclipse has this refactoring) 3) a The while loop is difficult to read, trace, and understand. And it is longer. The recursive solution can be easier to understand. Use the refactoring Replace iteration with Recursion to make more readable code. BTW: Worried about all of those method calls at runtime? A compiler can make the code to the left run as fast as the code to the right. And you should wait until you profile the code to see if this is a bottleneck 4) b When you have a complicated conditional (if-then-else) statement, use the refactoring "Decompose Conditional". Extract methods from the Boolean condition 10. Blue (if the question where what is your favorite color, but the question will be something else) 10. Butter Pecan (if the question where what is your favorite ice cream, the question will be something else) 5