where <username> (including the < and > symbols) should be replaced with your CS username. Once you have your project submitted, please fill out the Project Submission form.

You should include the following files in this directory:

• a jar file named project1.jar that includes all of the necessary *.class files to run your program

• a src directory with all of the *.java files necessary to compile your program

• a readme.txt file with your name, email address, student id, and brief description/justification of your approach
  

To continue and make good progress in this class, you should aim to complete this project by the suggested deadline. To be eligible to still receive an "C" project grade in this course, you must submit this project by the listed cutoff date. These dates for this project are:

Recall that you may only have one project submitted at any time, and you must allow two weeks after your submission date for grading.

Execution

Your code must run on the lab computers. If you are developing your code on a home computer or laptop, be sure to check out your code on a lab computer and test it. Your main method must be placed in a class named Driver. Your code will be tested using the following commands:

where <arguments> will be the following command-line arguments (in any order):

• -d <directory> where -d indicates the next argument is a directory, and <directory> is the directory of text files that must be processed
  

The output of your program should be a file invertedindex.txt that contains the contents of your inverted index in the following output format:

where the word is listed alone on a single line, followed by lines with the absolute file path, and a comma-separated list of locations. An empty line should separate entries.

If there are any issues with your submission and running your code, you will be asked to resubmit.

Functionality

For this program, you must traverse the supplied directory and process all *.txt files found in that directory (including all subdirectories). For each text file, you must parse out each word. For each word, you must store a mapping of the word to the file and position that word was found in a custom inverted index data structure. See below for details:

• Your inverted index must store a mapping from word to the file(s) it was found, and the position(s) in that file it is located. This will require nesting multiple data structures. You should choose these data structures wisely.
  
  
• The positions stored in your inverted index should start at 1. For example, if a file has words "apple banana carrot", then "apple" is in position 1, "banana" is in position 2, and "carrot" is in position 3.
  
  
• Your program must separate a file into words by any whitespace, including spaces, tabs, and new line characters.
  
  
• Your program must be case-insensitive. For example, the words APPLE, Apple, apple, and aPpLe should all be seen as the same word.
  
  
• Your program must ignore all characters except letters and digits. For example, the word "age-long" should be seen as "agelong" (since the dash "-" should be ignored) and the word "Hello!" should be seen as "hello" without the exclamation "!" mark. One way to accomplish this is to replace any special characters with the empty string before parsing.
  
  
• Your program must support large text files. As a result, you should not read the entire file into memory at once. It is, however, okay to read a single line from the file into memory at once.
  
  
• Your program must be designed to object-oriented. For example, you should separate directory traversing, file parsing, and data maintenance into different classes. 
  
  
• You must also protect the integrity of your inverted index, making sure you have proper encapsulation of any private data members. For example, do not return a reference to a private data member in a public method.

See the next section for recommendations on how to approach this project.

Getting Started

It is recommended you work on this project in two phases. For phase 1, you should:

• Build a basic directory traverser, that is capable of getting all the text files from a directory.
  
  
• Build a basic file parser, that is capable of splitting words by whitespace characters.
  
  
• Create a basic inverted index that stores mappings from words to files, but not positions.

For phase 2 of this project, you should:

• Modify your directory traverser to also get text files from all subdirectories.
  
  
• Modify your file parser to ignore special characters.
  
  
• Modify your inverted index to also store file positions in addition to files.

Of course, this is just a recommendation. You should try to tackle all projects iteratively, but you can decide how best to break the project into parts.

Project Hints

Here are some recently posted hints to help you on this project:

Testing

You should thoroughly test your own code. Make sure it meets the functionality requirements, performs proper exception and error handling, and produces the correct output. To assist you in your testing, several test files have been provided at the following location on the lab computers:

You should not submit your code until you are able to produce the test results. However, just because you produce the test results, does not mean your code is ready for submission. See the Projects page for what is required for the project to be considered "complete".

Note: For this particular project, the order of output may differ. However, the words and positions should not.