Checkstyle is a development tool to help programmers write Java code that adheres to a coding standard. It automates the process of checking Java code to spare humans of this boring (but important) task. This makes it ideal for projects that want to enforce a coding standard.
Checkstyle is highly configurable and can be made to support almost any coding standard. An example configuration file is supplied supporting the Sun Code Conventions. As well, other sample configuration files are supplied for other well known conventions.
A good example of a report that can be produced using Checkstyle and Maven can be seen here.
Checkstyle can check many aspects of your source code. Historically it's main functionality has been to check code layout issues, but since the internal architecture was changed in version 3, more and more checks for other purposes have been added. Now Checkstyle provides checks that find class design problems, duplicate code, or bug patterns like double checked locking.
For a detailed list of available checks please refer to the Standard Checks page.
The latest release of Checkstyle can be downloaded from the SourceForge download page.
If you want to live on the bleeding edge, you can checkout the current development code from Mercurial and compile yourself. Note, you will need to have the Mercurial EOL Extension enabled to ensure there are no issues with the line endings (this extension will make the files match the local operating system).
Checkstyle is most useful if you integrate it in your build process or your development environment. The distribution includes:
Additionally plug-ins are written by third-parties. Some of them are still based on the Checkstyle 2.4 release, although there have been many improvements since then. The known plug-ins are:
| IDE / Build tool | Main/Initial Author | Available from | Remarks |
|---|---|---|---|
| Sonar | Freddy Mallet (initial author) | Sonar Home Page | Demo site |
| Eclipse/RAD/RDz | David Schneider | Eclipse-CS Home Page | In 2007 was awarded Best Open Source Eclipse-based Developer tool . |
| Eclipse/RAD/RDz | Roman Ivanov | Project Page | Extension for Eclipse-CS plugin and also an incubator for Checkstyle checks that are not present in main stream of Checkstyle. See the Wiki and Blog . |
| Eclipse/RAD/RDz | Marco van Meegen | Checklipse Home Page | |
| IntelliJ IDEA | Jakub Slawinski | QAPlug | Provides quality assurance features. |
| IntelliJ IDEA | James Shiell | Checkstyle-idea Project Page | Provides real-time and on-demand scanning. |
| IntelliJ IDEA | Mark Lussier | JetStyle Project Page | |
| NetBeans | Petr Hejl | Checkstyle Beans | Problems with source code are displayed as annotations of the source |
| NetBeans | Paul Goulbourn | nbCheckStyle | |
| NetBeans | Software Quality Environment (SQE) | ||
| jCoderZ | fawkeZ | Combines multiple tools (CheckStyle, findbugs, PMD, Cobertura, etc.) | |
| BlueJ | Rick Giles | bluejcheckstyle home page | |
| tIDE | Built in | ||
| Emacs JDE | Markus Mohnen | Part of the standard JDEE distribution | |
| jEdit | Todd Papaioannou | JEdit CheckStylePlugin | |
| Vim editor | Xandy Johnson | Plugin Homepage | Vim file-type plug-in |
| Maven | Vincent Massol | Checkstyle supported out of the box | example report |
| QALab | Benoit Xhenseval | QALab Home Page | Supports tracking Checkstyle statistics over time. |
If you have written a plugin for other IDEs, please let us know, so we can provide a link here.