Any good Java linter? (unused return value)

Hello!

I'm looking for a good Java linter.

I was surprised to find that the top Google hits are hosted on sourceforge, don't have very many inspections and (in some cases) haven't had any releases in 2+ years.

Is there any up-to-date popular solution?

(Specifically I'm looking for a check that flags unhandled return values in some situations, but preferably as part of a mature package).

Many thanks!

Mark

EDIT: shortly after posting this, a colleague recommended Sonar, which seems to be the closest thing so far. Still open to suggestions.