Due: Monday, February 10, 4 PM (in class).

• (10 points) Replace the call

      game = (Game)(Class.forName(gameName).newInstance()); 
  

  in PlayGame.java by the call

      game = GameFactory.create(gamename);
  

  The best design hard codes Easy and then tries to load dynamically. The Exception thrown should be a GameException. PlayGame needs to be rewritten both the call the factory method and to catch the possible exception.

  Some of you submitted poorly formatted code and got a zero for this part of the assignment.

• (10 points) Think about whether there should be a PlayerFactory in the game package. Discuss the reasons for and against.

  Arguments for:

  • symmetry - treat Game and Player the same way
  • remove ugly code - after you see how nice PlayGame looks with the game factory you should want to build a player factory.

  Arguments against

  • If it isn't broken don't fix it.
  • Players are more likely than Games to be constructed outside the game package.

  The arguments for are much more convincing. I put a PlayerFactory into release 2 of the game package $CS680/games2.

• (10 points) Read about the singleton design pattern in Jia - pages 114 and 251.
  • Should the instances of class Game returned by the GameFactory be singletons?

    Probably not. That would work for now, when the application is single threaded and only one game can be played at a time. But perhaps when there's a GUI and certainly when there's a web interface multiple games can proceed simultaneously and singleton's won't work.

  • What is there about how the game package deals with PlayerNumber that resembles the singleton design pattern? In what ways is it different? (The point of this question is not to get a correct answer. It's to make you read through code that provides a type-safe way to create "symbolic constants" in Java, so that you will know how to do that in your own code.)

• (10 points) Study the code for the game package and its drivers. Comment on some part of the design you found interesting or instructive.

• (10 points) Draw a UML sequence diagram for the method call

     114                  m = ((ComputerPlayer)player).findbest(g);
  

  in PlayGame.java when the ComputerPlayer is an instance of class Speedy and the Game is Easy. (I haven't done this myself yet. It may be quite complex. If it gets too long, you may fudge some of the deeper stuff as long as you show clearly that you really understand how a UML sequence diagram works.)

• hard copy of the answers to the questions asked,
• hard copy of your Java source code, and
• a memo discussing your design and coding process. Where did you encounter problems? How did you solve them? What did you learn?

Leave source code in a hw2 subdirectory of your cs680 course directory. Do not alter any permissions.