The Checkstyle plugin version 3.x is using Checkstyle 4.x, allowing the use of the new features in Java 5.
The Checkstyle plugin version 1.x was using Checkstyle 2.x, the
2.x versions use Checkstyle 3.x. The Maven goals for the Checkstyle
plugins have not changed and the way to invoke it can either be
maven checkstyle or maven checkstyle:report.
Some properties have changed. The most
important change is probably the addition of a
maven.checkstyle.header.file one to point to your
License file.
The major migration step is to migrate your previous Checkstyle
properties (located in a properties file) to the new XML configuration
file introduced by Checkstyle 3.x. The new configuration is described
on the
Checkstyle
config page.
Once you have finished migrating your Checkstyle configuration, modify
the maven.checkstyle.properties property point to the
new XML file.