Harvey Mudd College
Computer Science 60
Assignment 6, Due Thursday, March 2, by midnight

Spampede!

Assignment 6 takes advantage of the double-ended Queue (Deque) class you wrote in assignment 5 in order to implement a centipede in search of spam within a simple Maze-like world. This will give you the chance to use Java's graphics library and event-handling code. The Java 1.1 event-handling mechanism will be used.

Example Applet

Files and Classes to Create

You will need to create a file Spampede.java that contains at least the following classes:

• a MazeCell class (the default class from assignment 5 is included)
• a Maze class (a stripped-down version of assignment 5's is included) that contains a two-D array of MazeCells named grid.
• a Deque class (such as the one you wrote last week)
• a DCell class (used in Deque)
• a Queue class (used in Deque)
• a QCell class (used in Queue)
• a Spampede class that extends the built-in Applet class in Java.

A copy of ExampleApplet.java is named Spampede.java in the /cs/cs60/as/a6 directory. To get it, the HTML file you will need, and a script for compiling and copying your Spampede applet, you can do the following:

cp /cs/cs60/as/a6/*Spam* ~/cs60/a06

OPnce you have done that, you should be able to compile Spampede and copy it to your public_html directory with the single command

./makeSpampede

What does the code have to do?

The particular applet behaviors and methods you need to implement are

• Drawing the maze and the centipede within it. Each MazeCell (the same as centipede segments) should be 10 pixels by 10 pixels. The default maze will be a simple room with a single vertical wall in the middle. The room will be 30 MazeCells by 50 MazeCells, the outer boundary of which consists of walls. This room will be provided in the Maze class within the /cs/cs60/as/a6/ExampleApplet.java file.



• Every 0.5 second, the centipede's position should be updated within the maze. That is, the centipede's head advances one MazeCell in whatever direction it is facing, and the centipede's tail retracts by one MazeCell. (You need not stick to this speed, but remember that the graders will be using your applet -- try to keep them happy!)



• If the centipede's head occupies a MazeCell that contains a wall or another part of the centipede, the centipede dies, and an appropriate consolation message should appear somewhere on the screen, or, if you prefer, the game should be reset to its starting conditions. (This is what the example Spampede applet does.)



• If the centipede's head occupies a MazeCell that contains a morsel of spam, the centipede grows by one MazeCell. That is, when the centipede next moves, its head advances one square, but its tail does not retract.



• When the user presses the following keys, the centipede should change direction as indicated:
  • r : reverse (switch directions)
  
  
  
  • i : turn up (north)
  
  
  
  • j : turn left (west)
  
  
  
  • l : turn right (east)
  
  
  
  • k : turn down (south)
  
  
  
  If the centipede is already heading in the direction that the user chooses, nothing changes. If the centipede changes direction so that it is moving back on itself (from South to North, say, or West to East), you may either reverse direction, ignore the change, or "terminate" that centipede. (The last is what the example applet does.) Note: the reverse (r) should work without dying in any case.



• Maintain Start and Pause buttons. Working versions are provided in ExampleApplet.java -- you will not have to change them, though you may "upgrade" them if you wish.

I want more!

If you haven't had enough of the Spampede.java file at the end of this assignment, there are a couple of specific items and an open-ended invitation to improve on the applet for up to 20% (or beyond...) optional bonus credit.

• Speed up: You might want to have the rate at which the centipede is moving to increase as the game progresses.



• Scoring: You might want to have a system of scoring with a runing total displayed as a label or text field or simply drawn to the applet panel.



• Lives: Rather than reseting after a single crash, keep a text field (or label) with the number of lives remaining and decrement it after each crash. When there are no lives left, stop the game (though you might want to consider a "reset" button.)
  
  
• Levels: Rather than maintaining a single, static maze, you may want to have the centipede advance to different mazes after comsuming enough spam.
  
  
• General improvements: Feel free to add additional features you think would enhance the Spampede! applet.
  
  

In addition, the extra credit for last week's assignment is extended through this week. If you would like to create an applet representation of the SpamSeeker (as indicated in that assignment), you may submit that in a separate file for additional credit.

Testing your applet

You can test your code in two ways:

1. With the appletviewer: if you are working in the terminal room or have an X connection to a remote machine, you can test your applet with the command

   appletviewer Spampede.html
   

   from any directory which contains both the compiled java code (Spampede.class, etc.) and the Spampede.html files, available for copying from /cs/cs60/as/a6.

   Caution! For me, turing's appletviewer takes a long time to appear and run (> 1 minute) unless the line

   setenv JAVA_FONTS "/usr/local/java/jre/lib/fonts"
   

   is added to my .cshrc file (which is then "sourced") before running. This line speeds the search for fonts, but error messages still appear that some fonts are not found.

   Appletviewer seems to process events very slowly in any case.

2. With a web browser: (preferred!)
   
   Documents you place in your public_html directory (which should be in your home directory) will be publicly available on the web. If you copy the files /cs/cs60/as/a6/ExampleApplet.html and the .class files (obtained by compiling) to your public_html directory, you will be able to view the ExampleApplet applet at URL http://www.cs.hmc.edu/~username/ExampleApplet.html, where username is replaced by your turing login name.

   A script for compiling and copying all the necessary files is available at /cs/cs60/as/a6/makeSpampede. You can copy that file into your directory and then run it as

   ./makeSpampede
   

   (You need the extra ./ if . (dot) is not in your path.

   Note Netscape will reload newly-compiled applet code if you hold down the "Shift" key while pressing the reload button. Internet Explorer will reload applet code if your hold down the "Ctrl" key while pressing the refresh button. (I suppose they're different to avoid lawsuits ... ?).

   Note #2 Netscape has a "Java Console" available from the Communicator -- Tools menu. You should have this open as you test your applet. With the Java Console, you can include System.out.println messages anywhere in your code and see what gets printed. In addition, runtime errors will get reported there. This is a good thing! Debugging without it is bad! (Spoken from first-hand experience.) I don't know how to use the Java Console on IE (if anyone does, please let me know.)

Reading

Submission

You should submit your Spampede.java source file in the usual way, i.e., by running

% cs60submit Spampede.java