(The submitter mistakenly thought the CommentMerge program would have
this capability.)

This program would take the API documentation of a JSR, e.g. the API
documentation of MIDP 2.0, and produce source files for all
public / protected classes with compilable stub methods
(e.g. they all throw new RuntimeException("not implemented yet").
 
  > Are you saying that if you have HTML files generated from
  > the Javadoc tool, that you would like to be able to generate
  > source stubs from that documentation?
 
yes. Correct.
 
  > Would it
  > copy doc comments to the destination as well as stubs?
 
That would be a great help when filling out the stubs :-).
 
  > We have a stubmaker doclet that generates source stubs
  > from source files. Would that help? Could the person
  > who owns the source files run this on their source code,
  > then send you the stubs?
 
We have two problems: start a clean room implementation given a
specification (maybe an early version). At this point, there is no
source available, and our competitors will not run your tool on their
source to produce stubs for us.
 
The second problem is more important, however. The spec develops, and we
get newer versions of it. It is very hard to read through every new
version and to check where some API changes took place. For this second
problem, we could use your tool with the -checkOnly option to compare
our implementation for compliance with the (newer version) of the API
documentation.
Note that this is not a "custom doclet" request, as originally submitted.
A doclet works on source files, by definition. This request is for a
an HTML-API to Source-Code-Stub generator.