• 7/28: Fixed output files for sample 2.
• 7/27: Don't forget to add comments describing any methods you write (see the Commenting Guide for more info).

We will model a forest as an n-by-n grid (e.g., a square 2D array), where each entry in the array represents a location in the forest. Each location represents one of three states:

• empty: the location contains no tree or a burnt tree
• tree: the location contains a non-burning tree
• burning: the location contains a burning tree

Here's an image of what an initial forest configuration might look like. In this image, empty is shown in yellow, tree is shown in green, and burning is shown in red. The example images show a forest that is 50 x 50.

How fire spreads

To model the spread of a fire, we define a function spread. At each step in the simulation, we apply spread to each location in the forest to determine its state at the next step. A location's state at the next step depends on the location(site)'s current state and the values of its neighbors to the north (N), east (E), south (S), and west (W).

The model uses different rules for different current states:

If a location is empty: it remains empty at the next time step.

If a location is burning: it will burn down in one time step, so it becomes empty at the next time step.

If a location is tree: it may or may not catch fire at the next step due to a fire at a neighboring site. Thus, it may be tree or burning at the next step. We explore this next.

Determining whether a tree catches fire: We must also consider that there is some probability, probCatch of a tree catching fire if a tree in a neighboring cell is on fire. If a location is tree and fire threatens the tree, probCatch is the probability that the tree will catch fire at the next time step.

Suppose that the probability of a tree catching fire is 15%; probCatch = 0.15. For each location representing the tree state, we generate a random number [0.0,1.0). On average, 15% of the time this random number is less than 0.15, while 85% of the time the number is greater than or equal to 0.15.

We use the following logic to determine if a tree catches fire:

if site is tree and (at least one of N,E,S,W are burning)
    if a random number between 0.0 and 1.0 is less than probCatch
        site burns
    else
        site remains tree
    

NOTE: In your program, you will use a class we have provided, RNG, for random number generation. RNG is very similar to the Dice class from Projects 2 and 3 and has a method next(boolean isPredictable); this method will return a double in the range [0.0,1.0).

Applying spread to each location in the forest

To run our simulation, we represent the passing of time and the state of the forest at each time step. At each time step, the simulation determines the state of each location at the next time step based on the state of each location at the current time. Thus, the program runs a simulation by counting time steps and at each one producing a new grid for the next time step.

We define a function applySpread that takes a forest and a probability of the fire spreading to a location (probCatch) and returns another forest with spread applied to each location in the forest. The function applySpread applies spread(site, N, E, S, W) to each internal location in the forest--that is, applySpread does not process the locations on the boundary. Boundary locations should remain unchanged in subsequent time steps.

Here are some images of what the forest might look like after some number of iterations. In these images, probCatch is 0.5.

1 step	2 steps	10 steps	50 steps

Main class

Your main class must be named ForestFire and contain a main method that will be used to launch your program.

Instantiable Classes

You must define at least one instantiable class as part of your program. How you design this class (or classes) is up to you.

Before you begin implementation, you should plan what instantiable class or classes you will build. What parts of this simulation would work well as Objects? Decide what methods and instance variables you will need for each class.

Each class must be defined in its own Java file.

The file format is the same for files that you read in and files that your program writes out:

• The first line contains the width and height of the forest, separated by a comma
• All other lines contain a "row" of the forest, where each location in the forest is specified as follows (locations are comma separated):
  • E - indicates the location is empty
  • T - indicates the location contains a tree
  • B - indicates the location is burning

Here's the contents of a sample file:

5,5
E,E,E,E,E
E,T,T,T,E
E,T,B,T,E
E,T,T,T,E
E,E,E,E,E

For the project, you may work in pairs. Both partners must be currently enrolled in CS 302-001. If you choose to work with a partner, you must follow the rules below. These rules are the same as for Project 2.

Rules for Pair Programming

• You may only have one partner for this project
• You may have a different partner for future projects
• You may not pair program with multiple partners on the same project
• Once you start working with a partner on a project, you must complete the project with that partner.
• You must list your partner as a collaborator in the header comments of your source files
• Only one partner will submit .java files via the Dropbox for this project. However, both partners must submit a README file that lists the full names of both partners
• You must follow the principles of pair programming summarized below

Principles of Pair Programming

Before you submit your work, check the following:

• Does your program contain a main class and at least one instantiable class?
• Is your main class named ForestFire in a file ForestFire.java?
• Are any instantiable classes you defined in their own Java files?
• Does your implementation of the spread function use the provided RNG class?
• Does your program catch all checked exceptions associated with File input and output?
• Does your program match the sample output?
• Does your program write out a new file of the specified format, with the specified name?
• If you used ForestFireGUI while developing your program, did you remove references to this class in the final version of your program?
• If you worked on your own computer, did you verify that your program works correctly on a lab computer?
• Did you follow the style and commenting guidelines?

To submit: