COMP 310 Spring 2010	Lec04: Ballworld Design, continued...

Assignment 1 homework instructions

Here are some optional, though potentially useful utility classes you may use or adapt in your code:

• ballworld.SineMaker -- A class that has methods that create sinusoidally varying numerical values, useful for situations where you want something to go up and down in size or value.   This class is not a Singleton, so multiple instances of SineMaker will run independently.

• ballworld.IRandomizer -- An interface that defines methods to return various random values,such as Point locations, velocities, colors, etc.

• ballworld.Randomizer --  A Singleton implementation of the IRandomizer interface.

• command.ILambda -- An interface specifying a generic Command object (lambda function).   Useful for call-back commands, etc.

• command.NoOpLambda -- A Singleton ILambda implementation that does nothing except return its input parameter.  Useful for initializing ILambda's to insure well-defined behavior at all times and eliminate problems with null pointer errors on uninitialized commands.

Inheritance-based Ballworld demo

Help Session?

Thursday afternoon, 1-4 PM in OEDK somewhere?   

Using the Java API resources:   Click the "Resources" button above and navigate to the "Comp310 Java Resources" page and follow the links to the Java API documentation.

Ballworld design:

• Issues that people have had in their attempts to get the code running so far?
• ABall methods and fields: consensus?
  • An object is defined by its behaviors.
  • What is the process to update a ball? 
    • What needs to be done?
    • Can the entire process be described in terms of concrete processes or not?
  • New ball instantiation issues:  what needs to be specified?
• What all do we need to create the whole system?
  • Ball hierarchy
  • GUI frame
  • Something to put it all together, a "controller".
    • Instantiate the GUI
    • Instantiate the dispatcher.
    • Instantiate and start the timer.
    • Supply the methods for loading balls, clearing balls, updating balls, etc.
    • How many call-back lambdas are needed to connect the controller to the GUI?
• Fundamental Design Principle:   The Separation of the Variant from the Invariant
• Design patterns:
  • Singleton  - in the utility classes above
  • Union - in the abstract-concrete ball heirarchy.
  • Observer-observable - in the dispatcher system
  • Template - in the ball updating method.

© 2010 by Stephen Wong