I'm afraid this is not Javadoc - but doxygen supports grouping elements in output.
I used doxygen in the Javadoc preference for personal projects, as well as for multilingual projects professionally. The format of the documentation comments is for the most part fairly close to Javadoc, but I found it much richer and more extensible, and the output is simply better.
Heck, for one project, we published the User Guide and API Guide in PDF format via doxygen ...
simon.watts
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