Sample repository to demonstrate differences in checkstyle import order checks between version 6.x and 8.9. In the old version, there was no error for import separation, while in the new version this is flagged as a violation.

To see the original behaviour, run

mvn checkstyle:checkstyle -Dcheckstyle.consoleOutput=true

To see the new violations, run

mvn checkstyle:checkstyle -Dcheckstyle.consoleOutput=true -Pcheckstyle8

The errors reported will be like these (local file paths may differ):

[INFO] --- maven-checkstyle-plugin:3.0.0:checkstyle (default-cli) @ checkstyle-poc ---
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Starting audit...
[ERROR] /Users/mdrob/IdeaProjects/checkstylepoc/src/main/java/Main.java:5: Extra separation in import group before 'com.foo.Foo' [ImportOrder]
[ERROR] /Users/mdrob/IdeaProjects/checkstylepoc/src/main/java/Main.java:7: Extra separation in import group before 'org.bar.Bar' [ImportOrder]
Audit done.
[INFO] There are 2 errors reported by Checkstyle 8.9 with src/main/resources/checkstyle.xml ruleset.

A checkstyle.xml file with <property name="separated" value="true"/> is also available, and can be used with the separated maven profile.

mvn checkstyle:checkstyle -Dcheckstyle.consoleOutput=true -Pcheckstyle8,separated

This version still flags a violation inside of the group:

[INFO] --- maven-checkstyle-plugin:3.0.0:checkstyle (default-cli) @ checkstyle-poc ---
[WARNING] File encoding has not been set, using platform encoding UTF-8, i.e. build is platform dependent!
[INFO] Starting audit...
[ERROR] /Users/mdrob/IdeaProjects/checkstylepoc/src/main/java/Main.java:7: Extra separation in import group before 'org.bar.Bar' [ImportOrder]
Audit done.
[INFO] There is 1 error reported by Checkstyle 8.9 with src/main/resources/checkstyle-separated.xml ruleset.