IntelliJ IDEA reports lots of code issues that could be improved. It would be good to address some of the more obvious items:

Unused imports
Unused code, often resulting from the File to Path conversion
Raw types, typically code that was used with older versions of JT Harness
Unnecessary semicolons
Unnecessary explicit type arguments
Use try with resources
Use lambda or method handles
Use List.of instead of Arrays.asList (but watch for null values)
Use multi-catch

Not all suggestions are removed in all cases; some are left as a matter of code style; some are left because of the need to support different JDK versions. There are probably other suggestions that could be applied as well.