1. Purpose
The purpose of this assignment is to implement a Stack ADT in the two most common ways, an array and a linked list. You will implement stacks for Java double numbers.
2. Description
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. You will write a program that reads a sound file in the .dat format and writes another .dat sound file which is the reverse of the first. The sample code has provided 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. The sample code has also provided an interface DStack, which defines a stack that holds double values. Your first job is to familiarize yourself with these files.
2.1. Implementing the Stack ADT
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. Reverse should work and create backward sound files once you complete these two 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. While there are convenient Java library methods for copying arrays, for this assignment, use your own loop to copy array elements manually (so you can "see" the work involved in copying).
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;
The only Java class that you should use to complete the implementations of your stacks is java.util.EmptyStackException. You should also use the length field of an array.
2.2. Running Reverse
The Reverse program takes 3 arguments (also known as "command-line arguments"). The first is the word array or list and specifies which implementation to use. The next two are the
input and output .dat file names (you need to include the .dat extension). Running the program will depend on your system; from a command line it will look something like:
java Reverse list in.dat out.dat
In an IDE there is usually a dialog box for setting program parameters which contains a field for the program arguments. (For example, in Netbeans select Build->Run Arguments and a bar will appear at the top of the screen that allows you to type in the arguments. Read more about setting command line parameters in Netbeans.)
To test your program, create short .dat files by hand to aid testing.
Note that Reverse.java just uses your stacks in one particular way: pushing a bunch of elements onto the stack and then popping them all off.
2.3. The .dat File Format
The .dat file format starts with one line describing the sample rate of the sound file. This line is required. The rest of the file is composed of two columns of numbers. The first column consists of the time (measured in seconds) when the sample was recorded, and the second column contains the value of the sample, between -1.0 and 1.0. This is the beginning of a sample .dat file. Notice that the numbers in the first column increase by 1/44100 each step. This is because the sample rate is 44.1kHz.
; Sample Rate 44100 00 2.2675737e-05 0 4.5351474e-05 0 6.8027211e-05 0 9.0702948e-05 0 0.00011337868 0 0.00013605442 0 0.00015873016 0 0.00018140590 0 0.00020408163 0
Note that all you need to do is implement the stacks, as the provided Reverse.java does file input/output for you. We are explaining the format because it will be helpful for writing short files by hand for testing purposes.
In order to play sounds you produce, you need a way to convert between the .dat format and a format that common media players (Windows Media Player, winamp, RealPlayer, etc.) understand, such as .wav.
sox allows you to convert to and from .dat sound files. The .dat files are useful because they are human-readable, text-based, sound files. Many versions of sox are available. You can download the one you need from https://sourceforge.net/projects/sox/files/sox/ by clicking on the folder for the most recent version (e.g., "Download sox-14.4.2-win32.exe (2.7 MB)") and then downloading the correct file for your operating system.
The Windows and Mac version are also a command-line program and work in the same way as the UNIX version described below. See below for some pointers on using it.
For those of you who are not familiar with command-line operations, here is how to use the sox program from Windows.
1. download the "sox12181" zip file from SourceForge. Unzip and extract the sox file to your desktop.
2. In windows: click Start -> All Programs -> Accessories -> Command Prompt. A command-line window should appear.
3. In the Command Prompt window, type: cd desktop
4. In the Command Prompt window: (with the sound file you wish to convert on the desktop as well), type sox secret.wav secret.dat
5. Now you should see the converted file secret.dat on your desktop.
The general strategy for using sox is as follows.
1. Take a .wav sound file of your choosing, e.g., mysong.wav. This sound shouldn't be longer than a few seconds, or your program will run out of memory.
2. Convert it to a .dat file: sox mysong.wav mysong.dat
3. Manipulate it with the program you will write: java Reverse list mysong.dat mysong-reversed.dat
4. Convert it back to a .wav file: sox mysong-reversed.dat mysong-reversed.wav
5. Listen to it with your favorite sound player.
That's all there is to it! You may send your reversed secret .dat file to your classmate and ask him/her to reverse it and find the original message
2.4. Questions
Submit a report (in word or pdf), answering the questions below.
1. How did you test that your stack implementations were correct?
2. 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.
3. Include a description of how your project goes "bonus components" the basic requirements (if it does).
4. What did you enjoy about this assignment? What did you not enjoy? What could you have done better?
5. What else, if anything, would you would like to include related to this homework?
2.5. Bonus Components (5 points) - Shrink the array when needed
The following suggestion is meant for you to try if you finish the requirements early.
Modify your array implementations so that when the array is 3/4 empty, the stack resizes to use an array of half the size.
2.6. Java Help
For this assignment you need to implement an interface, DStack, in two ways. The DStack interface defines a simple stack:
public interface DStack { public boolean isEmpty(); public void push(double d); public double pop();
public double peek(); }
An actual interface includes comments, including a description of how pop() and peek() should behave if they are called when the stack is empty. To implement this interface, write a class as follows:
public class ArrayStack implements DStack {
public ArrayStack() { // Your constructor code
}
public boolean isEmpty() { // Your isEmpty() code
}
public void push(double d) { // Your push() code
}
// continue with the rest of the methods,
// along with any fields, etc. }
The ListStack class should be defined similarly. You should include appropriate comments as needed. In particular, each file should begin with a comment that describes the class in the file, and includes your name and other identifying information.