Announcing that Checkstyle version 4.1 has been released and is available from See the detailed release notes at

The 4.1 release is a major upgrade and includes support for the Java 5 language. Everything still works just fine on Java 1.4 (and below) source code.

The other reason to upgrade are the numerous new checks and bug fixes. My favourite new check in the import control check ( which is used on a large project (40 odd developers) to ensure that the application layering rules are not violated.

Checkstyle supports out of the box running via an ANT task or the command line. Third-party plug-ins are available for Eclipse/WSAD, Maven, jEdit, NetBeans, Centipede, JBuilder, Emacs JDE, BlueJ.

The Eclipse plug-in authors have been very active in ensuring the Checkstyle 4.1 supports all the latest features. The Eclipse-CS plug ( has already released a version based on the 4.1 release.

Background: Checkstyle is a tool for performing analysis on Java source code. It is most infamous for performing syntax checks and enforcing coding standards. However, it is very flexible and includes checks for J2EE coding problems, Metrics analysis, Coding Problems, Class Design, etc. See

The Checkstyle architecture has been designed to allow custom checks to be easily developed. See for more details.

Plenty of documentation is available at