The Rabbit Hunt An example Java program The user interface The program design The eight classes RabbitHunt just gets things started Controller accepts GUI commands from user View creates the animated display Model coordinates all the actual work Bush just sits there Animal handles basic sight and movement Fox an Animal that tries to catch the rabbit Rabbit an Animal that tries to escape the fox RabbitHunt I public class RabbitHunt class variables private static Object field private static Model model private static View view private static Controller controller static int numberOfRows static int numberOfColumns RabbitHunt II public static void main String args numberOfRows numberOfColumns 20 field new Object numberOfRows numberOfColumns model new Model field view new View field controller new Controller model view Controller Creates the GUI buttons scrollbar field Handles user actions button presses moving the scrollbar resizing the window Enables and disables buttons as needed Alternately tells the model to make a move tells the view to display the results Displays a final message when the hunt ends View Displays the current state of the hunt that is the field and the things on it That s all it does Model Places the fox rabbit and bushes in the field Alternately gives the rabbit and the fox a chance to move Decides when the hunt is over and who won Provides several constants and a method for use by the animals A note about names I have named the central classes Model View and Controller to make the connection with the MVC model obvious I could have named them anything I wanted In this program the Model actually comprises five classes Model the boss class Animal and its subclasses Fox and Rabbit and Bush Why MVC is good The Controller class sets up lots of GUI stuff and handles it You haven t studied GUIs yet The View class does a lot of work you can probably figure out how View works None of this matters to your assignment Because the model is independent of the view and the controller you can totally ignore them Still you might learn something from them Directions Because Java does not define a direction type Model provides several constants N S E W the four main compass directions NE NW SE SW the four secondary directions MIN DIRECTION MAX DIRECTION in case you want a for loop that goes through all eight directions you probably will STAY a direction meaning don t move The turn method The Model class provides one direction method that you might find useful static int turn int direction int amount Given a direction and an amount to turn clockwise turn returns the resultant direction Examples turn Model N 1 returns Model NE turn Model N 2 returns Model W Other objects Model also provides constants for things you can see BUSH RABBIT FOX the obvious things EDGE the edge of the playing field In other classes such as Rabbit you can refer to these constants as Model BUSH Model FOX Model NW Model STAY etc The Bush class We ll start with the simplest class Bush What does a bush have to know What must a bush be able to do Here s the complete definition of this class public class Bush Believe it or not this is still a useful class Isn t Bush totally useless Please note this is not a reference to the current U S president With another program design a Bush might be expected to draw itself In MVC it doesn t even do that View does The program can and does create bushes The program can and does detect whether a square in the field contains a bush Creating and detecting Bushes To create a bush Bush bush new Bush Works because Bush has a default constructor To test if an object obj is a bush if obj instanceof Bush instanceof is a keyword used mainly like this This is all we do with the Bush class The Animal class Animal is the superclass of Fox and Rabbit Hence Fox and Rabbit have a lot in common You can get ideas about how to program a Rabbit by studying the Fox class Animal provides several important methods that can be used directly by any subclass Animal instance variables public class Animal private Model model int row int column The model gives access to several constants The row and column tell you where you are You may look at these variables but you are not allowed to change them I tried to make it impossible for you to change these variables but I didn t succeed Animal methods I int look int direction look in the given direction one of the constants Model N Model NE etc and return what you see one of Model BUSH Model EDGE etc Example if look Model N Model FOX int distance int direction returns how many steps it is to the nearest object you see in that direction if 1 you re right next to it diagonal steps are no longer than other steps Animal methods II boolean canMove int direction tells whether it is possible for you to move in the given direction false if that move would put you in a bush or off the edge of the board true if that move would be to an empty space true if that move would be onto another animal Good for the fox bad for the rabbit int decideMove The fox and the rabbit each have only one responsibility to decide where to move next The decideMove method does this decideMove returns an integer It can return one of the eight direction constants It can also return the constant Model STAY If decideMove returns an illegal move it is treated as Model STAY This doesn t seem like much but deciding a move is what you do in many games How the rabbit moves The rabbit is stupid int decideMove return random Model MIN DIRECTION Model MAX DIRECTION No wonder he gets eaten so often Wouldn t you like to help this poor stupid rabbit By the way random is a utility routine in Animal How the fox moves Each turn the fox starts by looking in every direction for the rabbit If the fox has not seen the rabbit it continues on in whatever direction it was last going If the fox sees the rabbit it remembers both the direction and the distance it moves directly to the spot where it last saw the rabbit if it gets there without seeing the rabbit again it just continues in the same direction The fox tries to dodge obstacles but if it can t it chooses a new direction randomly Looking around look all around for rabbit canSeeRabbitNow false for int i Model MIN DIRECTION i Model MAX DIRECTION i if look i Model RABBIT canSeeRabbitNow haveSeenRabbit true directionToRabbit i distanceToRabbit distance i Heading toward the rabbit if rabbit has been seen recently not necessarily this time move toward its last
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