Homework 9
Designing Classes

SI - Next session will give additional discussion of Homework 9.

Overview - The purpose of the homework is to provide practice in code reuse and refactoring. In the class diagram at right, a Player and Test class have been added, and the Game class has been simplified by moving Room responsibility to the Player class.

Getting started

• Open chapter07/zuul-better project file.
• Save project as HW9.

Assignment

1. Create a Test class to help in testing.
   • Create a new class Test with responsibility for a Game object,
   • add a test() method that issues commands to move from room to room, print help, and finally quit.
   • Use the following Test class definition as a starting point:
     
      

     public class Test {      Game game = new Game();      public Test() {}      public void test()     {         game.processCommand(new Command("go","south"));         game.processCommand(new Command("go","north"));         game.processCommand(new Command("quit",null));         System.out.println("Test done");     } }

   • Change the Game method:

     private boolean processCommand(Command command)

     to:

     public boolean processCommand(Command command)

   Test by:

   • Create a Test object,
   • execute the test() method.

   Should the game not quit properly after testing, you will not be able to compile.

   • Save the project, exit, and restart BlueJ or,
   • Reset Machine by pressing Ctrl+Shift+R.
      

2. Refactor the project to add a separate Player class.

   A Player object has responsibility for the player's current room.

   • Create a new class Player,
   • identify and factor out from Game class all Room class objects and methods,
   • place all the Room class objects, method definitions and references factored out of Game in Player class,
     • in simple cases, the field or complete method can be cut-n-pasted from Game to Player
     • when a Room object is referenced in a Game method (e.g. currentRoom), the code should be refactored to a new Player method and that method called from Game.
   • add a Player field to Game class,
   • the class diagram should appear as at right.
     • The arrows indicate that Game uses Player because of the Player field you added to Game.
     • To regenerate the arrows to show the current use:
       • Right click on the arrow and Remove.
       • Edit each class, making a trivial change, e.g. add a space at the end of a line.
       • Compile all the classes.

   Test by:

   • Create a Test object, execute the test() method.
   • Remember that you can play the game by creating a Game object and executing the play() method.
     
      
3. When the player quits, automatically display the path followed throughout the game.
   • In Player, use an ArrayList to add the current room to the path each time the player issues a valid go command,
   • In Game, on the quit command, print the short description of each room in the ArrayList,
     • add a Player class method to print the path list of rooms visited.

   Test by:

   • Create a Test object, execute the test() method.

    

4. Add the back command. This command does not have a second word. Entering the back command takes the player into the previous room.
   • Add back to the CommandWords for the command to be parsed,
   • add the back command in the Game processCommand() method,
   • implement moving to the previous room in Player class which has responsibility for the player's current room,
   • don't forget to add the current room to the path when the back command is processed,
   • add tests of the back command to the test() method.

   Test Game class by:

   • Create a Game object,
   • move into several rooms,
   • give the back command (test what happens if back is entered twice),
   • quit.

   Test Test class by:

   • Create a Test object,
   • execute the test() method.
      
5. Refactor the back command to move repeatedly back until the beginning room is reached.
   
   Hints:
   • Use an ArrayList, adding rooms when the go command is issued and removing rooms when the back command is issued.
   • Or use a Stack, you will need to find out about stacks through the Java documentation.

   Test by:

   • Create a Game object,
   • move into several rooms,
   • give the back command (test what happens if back is entered repeatedly),
   • quit.

    

6. Add to the Game class the method main() so that the program can be run outside of BlueJ. The method follows:
    

   public static void main(String args[])   {       ( new Game() ).play();   }

   Test:

   1. Compile in BlueJ.
       
   2. Open a Command prompt window.

      Start | Programs | Accessories | Command Prompt

   3. Change to the project directory using a command similar to:
      • cd \Users\username\blueJ\Hw10
         
   4. To execute the Game, enter:
      • java Game
         
   5. Capture the game screen as it is being played and paste to a Word file.

Turn in

C201 OnCourse Dropbox - Create a HW9 folder in the C201 OnCourse DropBox. Copy the following:

1. Test, Game, Player and CommandWords class JAVA files.
2. A Word file with Terminal Window printouts of a-e and Command Prompt Window of f.