PMD scans Java source code and looks for potential problems like:
You can download everything from here, and you can get an overview of all the rules at the rulesets index page.
PMD is integrated with JDeveloper, Eclipse, JEdit, JBuilder, BlueJ, CodeGuide, NetBeans/Sun Java Studio Enterprise/Creator, IntelliJ IDEA, TextPad, Maven, Ant, Gel, JCreator, and Emacs.
2013-05-01 PMD 5.0.4: minor version with lots of bug fixes (Changelog)
2013-04-05 PMD 5.0.3: minor version with lots of bug fixes (Changelog)
2013-02-03 PMD 5.0.2: minor version with lots of bug fixes (Changelog)
2012-11-28 PMD 5.0.1: minor version with lots of bug fixes (Changelog)
2012-05-01 PMD 5.0.0: major version supporting additional languages and new rules (Changelog)
Note: PMD 5 is not backwards compatible with PMD 4.x.
2011-11-04 PMD 4.3 (download):
The next development version will be PMD 5.1. We will release other 5.0.x versions with bug fixes if needed.
A snapshot of the web site for the new version is generated daily by our continuous integration server. Early access versions can also be downloaded from there.
A new snapshot of the 5.1 release is generated daily using a Jenkins continuous integration server.
Source and binary packages are available at http://pmd.adabolo.de/job/pmd-trunk/ in the artifacts section in the center of the page.
Maven packages are also generated regularly and uploaded to the snapshot repository and to Sonatypes OSS snapshot repository.