It's not that hard to do yourself. Use the java.util.jar.* package to load the entries from the library. Then take the file name for each entry, strip the .class and pass it to Class.forName(); On the result check for isInterface(); Then if it is create the stub class that implements it.
That isn't what I'm after.
I want a tool to generate a stub implementation of a given library, in other words a 'do-nothing' implementation.
And for the record the 'public interface' of a library is all the libraries public classes, interfaces, methods & members - not just the classes that fulfill the java definition of an 'interface'.
I can put together a tool to do it using javassist in a matter of hours; I was just expecting such a tool to already exist.
Oh well, I guess I'll write it, and put it up here.