1. Marine Biology Simulation Part III: Assignment, Milestone 2
Dung “Zung” Nguyen
Mathias Ricken
Stephen Wong
TeachJava 2004!
June 25, 2004

2. Rice MBS Assignment Milestone 1 Milestone 2 Part 1: KnightFish
Add a new fish species to the simulation
Part 2: WrappingEnv
Add a new kind of environment
Milestone 2
Part 3: Internals
Re-implement parts of the simulation framework
Part 4: Behavior Strategies
Refactor framework to allow dynamic behavior changes

3. Preparation Download materials for Milestone 2 Open DrJava
milestone2.zip
Unzip into empty directory
Open DrJava
Copy your drjava.jar into the project directory
Remove RiceMBSfw.jar from “Extra Classpath”

4. Part 3: Internals Open the DrJava_Test_* files tests package
Hit the test button
Several tests will fail
Critical portions of the framework have been removed
Tests provide students with feedback
Guide the way without giving away the answer
Better error messages than just “NullPointerException” and the like

5. Part 3: Internals Code missing in several places of the framework
Fish
Local environment
Global environment
Gives students a tour of the entire framework

6. Re-implement as per given specs.
Part 3: Internals
Re-implement as per given specs.
Pedagogy:
Modular design enables students to work on smaller pieces
Give jar files of framework to start
Students guided by unit test requirements
Exercises:
new fish, new environments
add features (e.g. breeding, eating, etc)
Re-implementation of initially supplied compiled classes.
Unit tests guide the way

7. Part 3: Internals Students gain insight into
Abstraction and loose coupling
Message passing
Writing large frameworks
Working with someone else’s code
Requires extensive work within existing framework
At the end of this part, students have completely restored the original functionality

8. Part 4: Behavior Strategies
Once students have understood the existing framework, they can improve it
Point out one of the flaws
Fish cannot change behavior
This part involves refactoring the old code and creating a new class hierarchy

9. Part 4: Behavior Strategies
Separate the variants
from the invariants
+ void move()
Strategy Pattern

10. Part 4: Behavior Strategies
Students have the opportunity to
Apply design patterns to improve the project
Refactor a substantial portion of the code
Experience how loose coupling makes this easy
Use unit tests to protect against previous bugs
Maintain documentation
Requires new design and code that augments existing framework
At the end of the assignment, students will have added a major feature to the simulation

11. Summary Students slowly gain experience with the framework
Parts 1 and 2 provides a lot of support
Part 3 gives students more responsibility, but unit tests provide guidance
Part 4 gives students freedom to design and improve
Compelling and entertaining example of object-oriented design