With PMD it's easy to add your own rules, something you will want to do sooner or later.
When selecting a tool I find it important that it integrates seemlessly into the build environment, whether that is
Ant, Eclipse, NetBeans or IntelliJ. Otherwise it just won't get used as much as it should be.
Other options you might look into are JCSC, Hammurapi, lint4j and jlint. My favorites are PMD and Hammurapi (which produces very nice reports that are cross-referenced with the source code).