Software Design (CSC-223 97F)

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Assignment Two: Racquetball Simulation

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 and to get your "feet wet" with Java programming.

Note: While we have not yet learned all the issues in Java programming necessary to do this assignment, we will have covered them by the end of class on Monday. In any case, you can begin the design of the program now, and fill in the details as you learn them.

Citation: This assignment is based on a column by Henry M. Walker to be published in the ACM SIGCSE Bulletin.

Turning it in: Leave your code in a publically readable directory, and email me the location of that directory. Note that your directory should include documentation generated by javadoc.

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.


Racquetball is a two-player 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.

One way to model the game is to assign a probability to each player winning a volley when he or she "has the serve." Write a Java program that takes these two probabilities, and computes the results of one thousand (1000) games between the two players. The results should include the number and probability of wins and shut-outs.

Your program should have at least the three classes

Extra Credit

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

Programming Information

While we'll cover general issues to support this type of application (e.g., loops and array), we may not cover all of the specific issues. Here are a few tips to help you over some of the programming hurdles.

Reading information

There is a good possibilitiy that we won't get to program input before this assignment is due. Hence, you will take input from the command line. You may recall that the main method of a class has one parameter, an array of strings. If you named that array args, you can refer to its elements as args[0], args[1], ... args[args.length-1].


You can convert a string to an integer with Integer.parseInt(String).

Random numbers

Java provides at least two ways to create random 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().

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().

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Disclaimer Often, these pages were created "on the fly" with little, if any, proofreading. Any or all of the information on the pages may be incorrect. Please contact me if you notice errors.

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