In order to build and run the Diff program, run the following command first:
> build

If Maven is not detected, then it will use wget to download Maven first (from here: http://maven.apache.org/download.cgi#Installation).  
Then, it runs "mvn clean package", which downloads all transitive dependencies, builds a jar file, and executing all unit tests.

Once this is done, you should be able to use the "jdiff.sh" script, which takes 2 parameters (the full paths to the source and target files to diff).

Usage:
> jdiff.sh /full/path/to/sourceFile /full/path/to/targetFile

------------------------------------

This program compares 2 files and outputs the lines and the line numbers where the files differ.

It's implemented as the Longest Common Subsequence (LCS) Problem, with a dynamic programming approach.

See the following article for a full description and example regarding LCS: http://en.wikipedia.org/wiki/Longest_common_subsequence_problem

The set of sequences is given by:
  lcs[i][j] = 0                              if i = M or j = N
            = lcs[i+1][j+1] + 1              if x[i]  = y[j]
            = max(lcs[i][j+1], lcs[i+1][j])  if x[i] != y[j]

Then, once we build the LCS matrix, we trace back through it so we can print out the diff types along the way.

The following rules apply when tracing back through the LCS matrix:
1) If we moved across M and N an equal amount, then this indicates a change ("c").
2) If we moved across N, but not M, then this indicates an add ("a").
3) If we moved across M, but not N, then this indicates a delete ("d").

------------------------------------

Here's an example (taken from: http://en.wikipedia.org/wiki/Diff):

> cat ~/tmp/file1
This part of the
document has stayed the
same from version to
version.  It shouldn't
be shown if it doesn't
change.  Otherwise, that
would not be helping to
compress the size of the
changes.

This paragraph contains
text that is outdated.
It will be deleted in the
near future.

It is important to spell
check this dokument. On
the other hand, a
misspelled word isn't
the end of the world.
Nothing in the rest of
this paragraph needs to
be changed. Things can
be added after it.

> cat ~/tmp/file4
This is an important
notice! It should
therefore be located at
the beginning of this
document!

This part of the
document has stayed the
same from version to
version.  It shouldn't
be shown if it doesn't
change.  Otherwise, that
would not be helping to
compress anything.

It is important to spell
check this document. On
the other hand, a
misspelled word isn't
the end of the world.
Nothing in the rest of
this paragraph needs to
be changed. Things can
be added after it.

This paragraph contains
important new additions
to this document.

> jdiff.sh ~/tmp/file1 ~/tmp/file2
0a1,6
> This is an important
> notice! It should
> therefore be located at
> the beginning of this
> document!
> 
8,14c14
< compress the size of the
< changes.
< 
< This paragraph contains
< text that is outdated.
< It will be deleted in the
< near future.
---
> compress anything.
17c17
< check this dokument. On
---
> check this document. On
24a25,28
> 
> This paragraph contains
> important new additions
> to this document.