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What Changed


This essay does not describe an existing computer program, just one that should exist. This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have prepared to help you is right here.

This project outline is not like the artificial, tidy little problems you are spoon-fed in school, when all the facts you need are included, nothing extraneous is mentioned, the answer is fully specified, along with hints to nudge you toward a single expected canonical solution. This project is much more like the real world of messy problems where it is up to you to fully the define the end point, or a series of ever more difficult versions of this project and research the information yourself to solve them.

Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; or give you any additional materials. I have too many other projects of my own.

Though I am a programmer by profession, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project in any way you please and to keep all the profits from your endeavour.

Please do not email me about this project without reading the disclaimer above.

I have a recurring nightmare. In it I have written some computer program that trashes my program files or my website files and I don’t notice. Or sometimes that files just quietly disappear and I don’t notice. The reality is not as bad as the dream, but the problem is still there. Windows file locking problems have often made files quietly disappear or become zero length.

This is a very simple program to calm that paranoia.

The program is given a constellation of directories and files to monitor. The first time it is run, it just prepares a summary file (or files) containing the names and sizes of the various files. The next time it is run it compares the current state of affairs with the old one and notifies the user of:

Then it replaces the summary file with a new one reflecting the current state of affairs. Every time you run it, you learn about the changes since the previous time it was run.


Most of the logic you can borrow from Untouch which detects even single bit changes in files. It recursively scans directories. You will need the CommandLine class. You will also need  File.exists, File. length and File. lastModified.

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