Extending the Case Study

1. Extending the Case Study Barbara Ericson ericson@cc.gatech.edu March 2006 Georgia Institute of Technology

2. Ways to Extend the Case Study • Subclass Fish • Add HungryFish that eat other fish when they are hungry enough • Add BottomFish that stay on the bottom • Add SickFish that spread disease to neighbors • Add non-Fish classes • Walls (extend AbstractDrawable) • Snorkelers (extend AbstractActionable) • Dolphins (extend Mammal) Georgia Institute of Technology

3. How to Subclass Fish • Create a new class that extends Fish • Like HungryFish • Add any fields needed by the new class • Add constructors that call super to initialize the inherited private fields • Override the act method • public void act() • Override generateChild to create this kind of fish • protected void generateChild(Location loc) • Add any methods needed by act() Georgia Institute of Technology

4. Adding Subclasses of Fish • Edit MBSGUI.java • Add the new class name to fishClassNames • String[] fishClassNames = {"Fish", "HungryFish", "DarterFish", "SlowFish"}; • Add a way to display the new class • Custom drawn one DisplayMap.associate("HungryFish", new RoundFishDisplay()); • Gif image DisplayMap.associate("SlowFish", new FishImageDisplay("smallfish.gif", Direction.EAST)); Georgia Institute of Technology

5. Adding HungryFish • Add a field to say how hungry this fish is • private int hunger = 0; • Add a field to say when ready to eat • private static final int NEED_TO_EAT = 5; • Override the act() method • Increase the hunger each time the method is called • If hungry enough eat a random fish neighbor • Move to the neighbor’s location and reset hunger to 0 • Otherwise use the inherited move method Georgia Institute of Technology

6. Fish and HungryFish Georgia Institute of Technology

7. Adding Non-Fish • The problem is the assumption in many classes that you will only have Fish or subclasses of Fish • To solve this I needed to change the GUI classes • So use mbsguigt.jar instead of mbsgui.jar in your classpath • Replace Fish, BoundedEnv, and MBSGUI, and Simulation Georgia Institute of Technology

8. Added Interfaces and Classes • Interfaces • Drawable inherits from Locatable • Actionable inherits from Drawable • New Classes • AbstractActionable the class to use to create non-fish objects that can act() and die() • AbstractDrawable the class to use to create non-fish objects that don’t act() • DrawableImageDisplay the class to use to display gifs for non-fish objects Georgia Institute of Technology

9. Sample New Classes • Added a Mammal Class • Need to come to the surface to breathe • Extends AbstractActionable • Added a Starfish Class • Which drops to the bottom and moves along the bottom • Extends AbstractActionable • Added an Orca Class • Extends Mammal Georgia Institute of Technology

10. Sample New Classes Georgia Institute of Technology

11. Adding Walls • The Wall class extends AbstractDrawable • Displayed by WallDisplay which just draws a filled rectangle • extends AbstractDrawableDisplay • Has an id, location, direction, color, and environment • Don’t act or die Georgia Institute of Technology

12. Walls Georgia Institute of Technology

13. Other Ways to Extend • Change the way things are drawn • Create new classes that extend FishDisplay like RoundFishDisplay and NarrowFishDisplay • Reuse environment classes for Checkers • Simulate a mouse in a maze • Some mice can move randomly • Smart mice can go towards the cheese Georgia Institute of Technology

14. Georgia Institute of Technology

15. For More Information • See http://coweb.cc.gatech.edu/ice-gt/165 • And http://coweb.cc.gatech.edu/ice-gt/166 Georgia Institute of Technology