JLearner is a Java-based Japanese character and vocabulary learning tool. It is mainly in German, and comes with vocabulary packages for the ikkyuu level 1 (highest "Japanese as a foreign language test"). It was written for university students who have be firm with all 2000 jouyou Kanji.
Jmol is a Free, Open Source molecule viewer and editor. It is a collaboratively developed visualization and measurement tool for chemical scientists. Jmol is an active project, and there are new features being added to it on a daily basis. Users are encouraged to modify it to fit their needs and to contribute their changes to the project.
JODE is a Java package containing a decompiler and an optimizer. The decompiler takes class files as input and produces something similar to the original Java file, and the optimizer transforms class files in various ways with can be controlled by a script file. It supports the following operations: Renaming class, method, field and local names to shorter or unique names or according to a given translation table, removing debugging information, removing dead code (classes, fields, methods) and constant fields, and optimizing local variable allocation.
Jonah is a two-part system for displaying headlines on your site. The backend fetches a list of My.Netscape or My.Userland style channel files, caches them locally, and generates a local html representation for each. The frontend provides an interface for viewing the generated headlines.