Computer Science Fundamentals (CS153 2004S)

Homework 6: A Raquetball Simulator

Assigned: Thursday, 8 April 2004
Due: Wednesday, 14 April 2004

Summary: Originally, object-oriented languages were designed to make simulation easier and perhaps more accurate. In this assignment, you will be developing a simple simulation of a racquetball game to consider some of the aspects of simulation.

Citation: This assignment is based on a column by Henry M. Walker be published in some issue of the ACM SIGCSE Bulletin, although it was designed before that issue was published.

Turning it in: Email me your .java files.

Collaboration: You may work in group of up to size two, and may discuss your design with any size group. You may also work with each other on general debugging issues.


Background: The Rules of Raquetball

Racquetball is a game played by two players on an indoor, enclosed court. One player serves the ball, the other returns (or attempts to return) the ball, and they continue to volley until one player misses. If the serving player wins the volley, that player receives a point. If the serving player misses the volley, the serve passes to the other player, and no points are scored. Play continues until the score is 11-0 (a shut out) or one player scores 21 points.

Basics of the Assignment

Your goal is twofold: First, write a program that narrates one match between two players. Next, write a program compute the liklihood of a player winning a game of Raquetball by simulating a large number of matches. Your second program should report at least four results, given two players, A and B: (1) the number of wins for A in the number of matches specified, (2) the probability of A winning, (3) the number of shut-outs (by either player) in the number of matches specified, and (4) the probability of a shut-out occuring.

Modeling Raquetball

In order to write both programs, you'll need to find a way to model various aspects of raquetball. The simplest technique is to assign to each player a probability of winning a volley when the player has the serve. To simulate a match, you start the serve with a player, determine whether or not that player wins. If so, you assign a point to that player for the match. If not, you switch the serve to the other player. For example, the output of a program that uses this model would be something like the following:

Jim serves.  Jim wins the point.  The score is now 1-0.
Jim serves.  Jim misses the ball.  Jane now serves.  The score is 1-0.
Jane serves.  Jane wins the point.  The score is now 1-1.
Jane serves.  Jane wins the point.  The score is now 1-2.
Jane serves.  Jane wins the point.  The score is now 12-21.
Jane wins!!!!

A more complex and more realistic mechanism is to assign to each player a probability of returning the ball. I assume you can figure out how to use this probabilty. If you choose this mechanism, your description of the game can also be more interesting (although it need not).

Jim serves.  Jane returns.  Jim returns, but barely.  Jane misses.
  The score is now 1-0.
Jim serves.  Jane returns easily.  Jim returns easily.  Jane returns aggressively.  Jim misses.  
  The score is 1-0.
Jane serves. ...

Of course, when you're doing the second part of the assignment (gathering statistics), you should not print this output.

Required Classes

You must create at least the following five classes for the two parts of the assignment.

Extra Credit

If you'd like some more to do on this assignment, you might consider one or more of the following:

Related Topic: Random Sequences of Numberse

In order to simulate the match, you'll need a random sequence of numbers. Java provides at least two ways to create random sequences of numbers, one from the Math class, and one from a separate Random class.

If you call Math.random() (that is, the class method random of the Math class), it will return a pseudorandom number between 0.0 and 1.0.

If you create an instance, r, of class Random, using something like

Random r = new Random()

you can ask for r.nextDouble(), r.nextFloat(), r.nextInt(),, or r.nextLong().

By pseudorandom I mean that it is generated algorithmically, but it is still hard to predict. On most (all?) computers, random numbers are generated using a random number generator, an algorithm for computing a random-looking (but not truly random) sequence. For some simulations, it is important that you get the same sequence of random numbers each time. You can seed the random number generator with r.setSeed().



Tuesday, 1 April 2003 [Samuel A. Rebelsky]

Thursday, 8 April 2004 [Samuel A. Rebelsky]


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