Barnes and Kolling Chapter Eight Questions
Barnes and Kolling Chapter Eight Questions
1 | Open the project dome-v1. It contains the classes exactly as they were discussed in the text. Create some CD objects and some video objects. Create a database object. Enter the CDs and videos into the database, and then list the database contents. | Done |
2 | Try the following. Create a CD object. Enter it into the database. List the database. You see that the CD has no associated comment. Add a comment to the CD object on the object bench (the one you entered into the database). When you now list the database again, will the CD listed there have a comment attached? Try it. Explain the behavior you observe. | CD: Death Magnetic (70 mins) Metallica tracks: 12 <no comment> CD: Death Magnetic (70 mins) Metallica tracks: 12 Great album it seems to add the comment string to the database class, we may infer that database class responds to other class changes |
3 | Draw an inheritance hierarchy for the people in your place of study. | Jonathan --> Daly--> Jackover--> WBAIS board--> Lord Almighty |
4 | Open the project dome-v2. This project contains a version of the DoME application rewritten to use inheritance, as described in the text. *Note that the class diagram displays the inheritance relationship. Open the source code of the Video class and remove the "extends Item" phrase. Close the editor. What changes do you observe in the class diagram? Add the "extends Item" phrase again. | The arrow connecting DVD to item is gone! I added it back on, thank god! |
5 | Create a CD object. Call some of its methods. Can you call the inherited methods(for examplesetComment())? What do you observe about the inherited methods? | The methods are inherited from other classes. |
6 | Set a breakpoint in the first line of the CDclass's constructor. Then create a CD object. When the debugger window pops up, use Step Into to step through the code. Observe the instance fields and their initialization. Describe your observations. | The debugger took me to the item source code. |
7 | Open the dome-v2 project. Add a class for video games to the project. Create some video game objects and test that all the methods work as expected. | public class VideoGame extends Item { private String gameName; private int numberOfPlayers; public VideoGame(String theTitle, int time) { super(theTitle, time); gameName = theTitle; numberOfPlayers = time; } /** * @return The artist for this CD. */ public String getgameName() { return gameName; } /** * @return The number of tracks on this CD. */ public int getNumberOfPlayers() { return numberOfPlayers; } } |
8 | Order these items into an inheritance hierarchy: apple, ice cream, bread, fruit, food-item, cereal, orange, dessert, chocolate mousse, baguette. | apple, orange are subclass of fruit cereal, baguette are subclass of class bread chocolate mousse, ice cream are subclasses of class dessert all of these all subclasses of super classes food-item |
9 | In what inheritance relationship might a touch pad and a mouse be? | touch pad-->mouse |
10 | square -> rectangle (every square is a rectangle but not every rectangle is a square) | |
11 | Assume we have four classes: Person, Student, Teacher & PhDStudent. Teacher and Student are both subclasses of Person. PhDStudent is a subclass of Student. Which of the following assignments are legal and why? Person p1 = new Student(); Person p2 = new PhDStudent(); PhDStudent phd1 = new Student(); Teacher t1 = new Person(); Student s1 = new PhDStudent(); s1 = p1; s1 = p2; p1 = s1; t1 = s1; s1= phd1; phd1 = s1; | |
12 | Test your answers to the previous question by creating the classes mentioned in that exercise, and trying it out in BlueJ. | |
13 | What has to change in the Database class when another item subclass (for example classVideoGame) is added? Why? | |
14 | Use the documentation of the standard class libraries to find out about the inheritance hierarchy of the collection classes. Draw a diagram showing the hierarchy. | |
15 | Go back to the lab-classess project from chapter 1. Add instructors to the project. Use inheritance to avoid code duplication between students and instructors. | |
16 | Draw an inheritance hierarchy representing parts of a computer system (processor, memory, disk drive, CD drive, printer, scanner, keyboard, mouse, etc.) | |
17 | Look at the code below. You have four classes (O,X,T and M) and a variable of each of these. O o; X x; T t; M m; The following assignments are all legal. m = t; m = x; o = t; The following assignments are all illegal. o = m; o = x; x = o; What can you say about the relationships of these classes? | |
18 | Draw an inheritance hierarchy of AbstractListand all its (direct and indirect) subclasses, as they are defined in the Java standard library. | |
No comments:
Post a Comment