Groovydoc to generate docs for java classes

Looking at the Groovydoc dsl reference ( I see that it should be possible to have groovydoc document my Java classes as well (I have a mixed-language project). That being said - I want my Java classes to remain in src/main/java and not move them to src/main/groovy. I’ve tried adding as a source to the Groovydoc task but it doesn’t seem to work.

Any way I can accomplish this?