Please note that the release is currently in a “Pre-alpha” state which means it only does the basic things and can ruin your music.
Requirements:
Need 64MB RAM
Java SE 6 or higher
You can download JAlbumGetter at the Sourceforge site.
The jar also contains the source code.
To use it, you just have run the jar file and it will ask for a directory. The app will then recursively go though each mp3 file and find album art for it using yahoo search. It works like a script so there is no interaction. If you launch it from the terminal, you can see where it is downloading from and when it is done. Interactivity is set to be in the project in a much later time.
The code for JAlbumGetter is GNU, but uses many other projects with different licenses.