CSE332 Summer 2010: Project 1 - Sound Blaster!

Outline

• Preliminaries
• Introduction
• The Assignment
  • Write-Up Questions
  • Above and Beyond
• Turn-in
• Acknowledgments

Due Date and Turn-In

Wednesday June 30th, 11pm: You can turn it in using Drop-box; the link's below under 'Turn-in'

Be sure to read the turn-in info before you submit!

Preliminaries

• Complete this project by yourself (i.e., without a partner). You may discuss the assignment with others in the class, but your solution must be entirely your own work.
• Download these files into a new directory:
  • You'll need these files to start out: Reverse.java, DStack.java, GStack.java
• The code provided for you will read in a sound file, but it does so in .dat format. You'll use a program called sox to convert wav files to .dat: You can find information on it here
• Later, when you are ready to run your program and the sox program, you will want these sound files: bot.wav secret.wav

Introduction

The purpose of this project is to implement a Stack ADT in the two most common ways, an array and a linked list. First, you'll implement stacks for Java double numbers. Then, you'll implement generic stacks and instantiate them with type Double.

Your Stack implementations will be used to do sound manipulation, namely reversing a sound clip. This process, called "backmasking," was used by musicians including the Beatles, Jimi Hendrix, and Ozzy Ozbourne, although it seems to have fallen out of favor in recent years. Click here for a history of this (sometimes controversial!) practice. "But wait," you say, "CSE 143 never taught me how to work with music..." Don't worry! All the music-handling parts have been done for you.

Even though the music-reversing code will use your stack implementations in only certain ways, you should test that your stacks are correct in all cases, not just those used by the reverse program.

The Assignment

You will write a program that reads a sound file in the .dat format (explained below), and writes another .dat sound file which is the reverse of the first. We provide you with a class Reverse whose main method reads in a .dat sound file, pushes all the sound values on a stack, then pops them all off and writes them into a new .dat sound file. We've also provided you interfaces DStack (for Part 1) and GStack (for Part 2), which define the stacks you will implement. Your first job is to familiarize yourself with these files.

Part 1

To begin with, you need to provide two stack implementations, one using an array and one using a linked list. They should be called ArrayStack and ListStack, respectively. They should implement the DStack interface given to you. Once you provide these implementations, Reverse should work and create backwards sound files. It should take no more than a page or two of code to provide the implementations. Your array implementation should start with a small array (say, 10 elements) and resize to use an array twice as large whenever the array becomes full, copying over the elements in the smaller array. Both ArrayStack and ListStack should throw an EmptyStackException if pop() or peek() is called when the stack is empty. To use EmptyStackException, add the following line to your file:

import java.util.EmptyStackException;

Note that your solution to Part 1 does not require making changes to Reverse.java.

Part 2

For part 2, you need to provide two more stack implementations, these implementing the interface GStack<T>. Create classes called GArrayStack and GListStack that are just like ArrayStack and ListStack except that they are generic in the type of elements kept in the stack. The simplest approach is to copy ArrayStack and ListStack and then make appropriate changes. Normally such copy-and-paste is poor form, but here the pedagogical purpose is to show you how little you need to change to make the code generic — and we want to grade all four stack implementations.

To use your generic stacks you will need to make some additions to Reverse.java by replacing the 3 occurrences of:

System.err.println("no support for generics yet");
System.exit(1);

with appropriate code. Again, the code you write will be only slightly different from non-generic code that is already there. Do not make other changes to Reverse.java.

Running Your Program

The Reverse program takes 4 arguments (a.k.a. "command-line arguments"). The first is the word array or list, and specifies which implementation to use. The second is the word double or generic; the latter is for Part 2. The next two are the input and output .dat file names (you need to include the .dat extension). From the command-line, you can run the program with something like:

java Reverse list double in.dat out.dat

To run your program in Eclipse, create a "Run Configuration" and under the "Arguments" tab put the arguments (e.g., list double in.dat out.dat) in the "Program arguments" box.

To test your program, you will need a .dat file, which you can create from a .wav file as explained in the Digital Sound section. It may also be useful for you to create some short .dat files by hand to aid testing.

Write-Up Questions

Turn in a report answering the following questions

1. Who and what did you find helpful for this project?
2. How did you test that your stack implementations were correct?
3. The file secret.wav is a backwards recording of a word or short phrase. Use sox (or another converter) and your program to reverse it, and write that as the answer to this question.
4. Did you use any classes from the Java framework or other class library? (Remember, as stated in the programming guidelines, if the answer to this question is anything other than "no", you may get a low score on this project if you use the library to implement your stacks!)
   (Addendum: it's okay to use java.util.EmptyStackException!)
5. Your array stacks start with a small array and double in size if they become full. For a .dat file with 1 million lines, how many times would this resizing occur? What about with 1 billion lines or 1 trillion lines (assuming the computer had enough memory)? Explain your answer.
6. Let's pretend that, instead of a DStack interface, you were given a fully-functional FIFO Queue class. How might you implement this project (i.e., simulate a Stack) with one or more instances of a FIFO Queue?
   Write pseudocode for your push and pop operations. Refer to the Written-Homework Guidelines for instructions on writing pseudocode. Assume your Queue class provides the operations enqueue, dequeue, isEmpty, and size.
7. Why would a stack implementation using a queue, as you described in the previous problem, be worse than your array and linked-list stack implementations?
8. In the process or making your generic stack implementations from your non-generic ones, what sort of errors did you encounter and how did you resolve them?
9. In hindsight, how much did you have to understand about the code in Reverse.java to make the changes to use your generic stacks?
10. Include a description of how your project goes "above and beyond" the basic requirements (if it does).
11. What did you enjoy about this assignment? What did you hate? What could you have done better?
12. Anything else you would like to include?

Going Above and Beyond

The following list of suggestions are meant for you to try if you finish the requirements early. Recall that any extra-credit points you earn for these are kept separate and will be used to adjust your grade at the end of the quarter, as detailed in the course grading policy. Note: please turn in all extra credit files separately, as described under 'Turn-in'.

• (1 point) Modify your array implementations so that when the array is 3/4 empty, the stack resizes to use an array of half the size.
• (2 points) Implement the Karplus-Strong algorithm (to generate "reverb" sounds). A description of this algorithm is available here.
• (5 points) Assuming that your .dat input file contained a single note, try writing a program which will output a single-octave scale beginning at that note. Would the notes of an "evenly spaced" scale grow logarithmically, linearly, polynomially, or according to some other function? For more information about the evenly-spaced scale, refer to this article. To earn full credit, you must start from an actual recorded note (not a synthetic one) and generate the single-octave scale. It's fine if the note durations are decreasing.

Turn-in information

• Turn in your assignment here
• Each file you turn in should have your name at the beginning. All text files should have your name on the first line; your name should appear in the comments at the beginning of each source code file you turn in.
• You must implement the list and array stacks by hand. You may not use any classes from the Java libraries to do the work. You should not use any import statements, except for java.util.EmptyStackException.
• You should turn in the following files, named as follows:
  • ArrayStack.java
  • ListStack.java While it is acceptable to submit a separate file for your node class, try using an inner class.
  • README.txt Answers to the Write-Up Questions.
  • Reverse.java
  • GArrayStack.java
  • GListStack.java
  • Any additonal files for the extra credit in a zip file named extracredit.zip. Please make sure that this zip file decompresses its contents into a folder called extracredit and not into a bunch of individual files.
  • Do not turn in DStack.java or GStack.java. You must not change these files. Your stack implementations must implement these interfaces as provided to you.

Sound and Sox

Acknowledgments

Like many assignments, this has been passed down to us through the vaporous mists of time. Among all our fore-bearers, we would especially like to thank Ashish Sabharwal, Adrien Treuille, and Adrien's Data Structures professor, Timothy Snyder.