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

Rice MBS Assignment Target Audience Students at the end of an objects-first CS2 Length of Assignment Two milestones Approximately 10 hours of work Probably supported by one or two labs

Studying the Case Study SimpleFish UnboundedEnv Variant Fish Behavior Variant Environment Behavior Re-implement as per given specs. White-box Framework: Extension by Subclassing

Strategy Pattern + void move() Static Behavior! Separate the variants from the invariants Studying the Case Study

Rice MBS Assignment Milestone 1 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

Preparation Read assignment document Download materials for Milestone 1 milestone1.zip Unzip into empty directory Open DrJava Copy your drjava.jar into the project directory

Configuring DrJava Add RiceMBSfw.jar file to “Extra Classpath” Edit, Preferences, Resource Locations Click on “Add” button Click on RiceMBSfw.jar file and “Select” Click on “OK” at the bottom of the dialog Now the framework has been added and can be used without source Make sure you run in “Full Java”

Running the Simulation In the “Interactions” pane, type java controller.MBSController Play around with the simulation Create new environment Edit environment Add fish Run simulation

Part 1: KnightFish Randomly pick one of 8 targets Example:

Part 1: KnightFish Turn into right direction Attempt one step forward If blocked, done If open, go there 3

Part 1: KnightFish Attempt a second step If blocked, done If open, go there Turn into right direction 3

3 Part 1: KnightFish Attempt the third and last step If blocked, done If open, go there

3 Part 1: KnightFish Moves almost like a knight, except… No jumping If blocked, might stop on the way Stop here

Part 1: KnightFish Complicated behavior Procedural programming: many nested if- statements Delegation method Nested visitors Cannot forget to handle a situation (compiler error!) Process flow diagramming Makes designing complex algorithm a systematic process

Part 1: KnightFish Students do this assignment Most of the code can be taken from existing examples For lack of time, we will do something simpler Fish attempts to move forward If blocked, turn around 180 degrees If open, go there Open TeachFish.java in model.fish

Part 1: KnightFish protected void move() tryMoveFwd(, ); } new ILambda() { public Object apply(Object moveCmd) { ((ILambda)moveCmd).apply(null); return null; } } Command to execute if blocked Command to execute if unblocked new ILambda() { public Object apply(Object notUsed) { turnRight(Math.PI); return null; } Ask local environment to move forward ((ILambda)moveCmd).apply(null); Tell the local environment to actually move the fish

Part 1: KnightFish Compile the file Run the simulation Create a new environment, and edit it Add a fish Select “Add…” Enter model.fish.TeachFish and hit “Create” Click somewhere on the map Run the simulation New fish class loaded at runtime!

Part 2: WrappingEnv Grid-based, bounded, and rectangular environment If the fish leaves on one side, it re-enters from the other side Topology: torus (donut)

Part 2: WrappingEnv Very similar to BoundedEnv In BoundedEnv, the Location class computes a neighboring location by adding a direction vectorto its own coordinates. The new coordinates might be inside or outside the environment. Can new coordinates ever be outside in WrappingEnv? Answer is part of class assignment and has been removed

Part 2: WrappingEnv The leftmost x-coordinate that is still inside the environment is 0. The rightmost one is (width-1). In BoundedEnv, the x-coordinate of the neighbor from there to the left is -1. What’s the x-coordinate of the left neighbor in WrappingEnv? Answer is part of class assignment and has been removed

Part 2: WrappingEnv The necessary changes are centralized in a single method, WrappingEnv.Location.getNeighbor. Since BoundedEnv and WrappingEnv are so similar, what OO technique can we apply to maximize code-reuse? Answer is part of class assignment and has been removed

Part 2: WrappingEnv Need to write constructors The framework uses factory methods Abstract creation To complete the environment, we have to override the factory methods WrappingEnv.makeLocation WrappingEnv.makeEnvFactory (code provided for makeEnvFactory) Students’ code is still based on existing code, but cannot simply be copied and modified anymore

Part 2: WrappingEnv Open WrappingEnv.java in sysModel.env The project was split into “model” and a “sysModel” packages to clearly separate system code (environments) from user code (fish) Fish more likely to get changed than environments Edit the WrappingEnv.Location.getNeighbor method Students would have to do a little bit more

Part 2: WrappingEnv Code is part of a class assignment and has been removed

Part 2: WrappingEnv Compile the file Run the simulation Create a new environment Select “Add…” Enter sysModel.env.WrappingEnv and hit “Create” Pick a size and create the environment Add fish Run the simulation

End of Milestone 1 Students submit code for Part 1 and Part 2 Material for Milestone 2 gets released after submission deadline Contains solutions for Milestone 1