Gjdoc is a documentation generation framework for java source files;
espcially generating API documentation in HTML format from
doc comments in source code.
Also, ANTLR (ANother Tool for Language Recognition) is used; this is
a language tool that provides a framework for constructing recognizers,
compilers, and translators from grammatical descriptions containing
Java, C#, C++, or Python actions. 

WWW: http://www.gnu.org/software/classpath/cp-tools/
     http://www.antlr.org/