Hello @HAYOUNGCHOI ,
The JUtils class is not available in the classloader for custom rules. When writing custom rules, you can only use what is coming from org.sonar.plugins.java.api. All the rest will make your code crash at runtime. When copy-pasting from existing rules, make sure that there are no such dependencies. I would advise you to re-read this part of the tutorial: What you can use, and what you can’t.
Looking at the code of isPrimitiveWrapper(), I’m pretty sure you don’t need anything particular from this. I would advise you to simply duplicate the method and the map it uses directly into your rule.
Cheers,
Michael