Open Checkstyle project in Eclipse

Checkout checkstyle sources and build them.

hg clone http://checkstyle.hg.sourceforge.net:8000/hgroot/checkstyle/checkstyle
cd checkstyle
mvn install

Please take a look at at output what version is installed [INFO] ................... checkstyle-5.7-SNAPSHOT.jar Where "5.7-SNAPSHOT" is a Checkstyle version.

Continue:

mvn jar:test-jar install

generate Eclipse project file ".project" for checkstyle:

mvn eclipse:eclipse

Now you can import project to Eclipse.