-- Getting Started --

There are only a few things you need to do to get up and running using the Checkstyle plug-in. The first thing is to understand a few basic concepts about how the plug-in works.

Basic Concepts
The Checkstyle Plug-in uses a project builder to check your project files with Checkstyle. So whenever you build your project your files will be checked by Checkstyle as well.
This goes so far that even if you edit a single file in your Eclipse editor this file will immediately get checked by Checkstyle on file save (assuming the Eclipse auto-build feature is enabled) - giving you immediate feedback about the changes you made.
To use a simple analogy - the Checkstyle Plug-in works very much like a compiler but instead of producing .class files it produces warnings where your code violates the Checkstyle rules.
The violations Checkstyle finds in your code are accessible in the Eclipse Problems View and are additionally annotated in the code editor.

The set of rules used to check your code is not fixed but highly configurable.
A Check Configuration specifies which check rules you want to inspect your code, the configuration settings for each rule, and the severity level of the message if the rule finds a problem.
Once defined a Check Configuration can be used across multiple projects. The Checkstyle Plug-in comes with one Check Configuration already defined.
You can create own Check Configurations using the comfortable Check Configuration Editor that comes with the plug-in or even use an existing Checkstyle Configuration file from an external location.

Got it, how to go on from here?
To learn how to set up a project to use the Checkstyle Plug-in read here - how to create your own check configuration read here .