Assignment 21

Task

Recreate a missing class from specifications.

Concepts: Practice with arrays, exceptions, writing classes, as well as reading and creating javadoc pages and working as part of a larger project.
Textbook: 10.5

Scenario

It's a quiet Wednesday afternoon at your job at Exitech when your boss dashes up to your cubicle, hair and tie in disarray:

We can't find Henry! And one of his files is missing from the server! I need you to rewrite it, quick!

See, we're working with this small independent gaming company and they want to produce some simple web-based shooting games with a focus on resource management. So Henry wrote this pistol class for them to reuse, and then a proof-of-concept game with vampires or something to show how it could be used. We've got the game, the testing classes, all the documentation... but the gun file's missing, and so nothing works!

I'll get Pam to forward what we have left. I need that class written by tomorrow morning!

Your boss dashes off before you can ask any questions. Ugh... not again!

A few minutes later, you recieve the following files from Pam:

• RevolverTester.java
• ZombieHallway.java

And a link to this documentation.

Steps

Reconstruct the Revolver class. The documentation should tell you what it does, and the RevolverTest should pass all tests when you're done. (You can copy and paste the documentation text to reconstruct the javadocs.)

Once RevovlerTest is working, you shouldn't have to touch ZombieHallway.

When you're done, rename Revolver.java to UsernameA21.java and submit it.

Hints

• I recommend using an array to simulate the gun's cylinder of 6 chambers.
• You may want to use some sort of index variable to represent the firing pin. "Spinning" the cylinder can then by done by setting the firing pin to a random index in the array. You can also safely advance the cylinder using modulus:

    this.firingPin = (this.firingPin + 1) % this.chambers.length;
  

• Revolver uses a couple existing exceptions from java.lang, so you do not need to write your own exception classes.

What to Submit

Upload your UsernameA21.java file to Tamarin.

Grading [6 points]

1 - Compiles + Coding Standards

Your program compiles successfully (no errors). Your code follows Java coding standards.

4.4 - Constructor and 9 methods

Each member works as described, with the given method signature, returning the correct values or throwing the specified exceptions when appropriate. (0.5 each; except open, close, and isOpen, which are 0.3 each).

0.6 - Encapsulation

All instance variables are private.

FAQs

How do I throw the exceptions? Does that happen automatically?

You need to explicitly test whether the exception should be thrown and then construct a new excption object and throw it.

So, for example, assume you're using a private boolean instance variable open to track whether the gun is currently open or closed. At the start of your fire() method, you could use this code:

  if (this.open) {
    throw new IllegalStateException("Cannot fire an open gun.");
  }
  //if made it this far, gun is closed, so put the rest of your fire() code here

The excpetion message is optional, so you could just have this instead: throw new IllegalStateException();