How to append the root directoory to the classpath

[XiaoluJiayou]

Hello, BruceEckel! When I run the code in Intellij IDEA will generate errors. But you have saying that append the root directory to the classpath will take it. So, How to setting the correct directory in my CLASSPATH. Could you give me a example , Thank You !!!!!

[Gehbt]

Here is my manually method in IDEA v2023.2.1:
File-> Project Structure -> Project Setting.Modules ->[unfold 'OnJava8-Examples'] -> ITEM.main -> [edit 'Source Folders' to that ITEM-NAME]
next you can follow by linter(eg, add package name to head).

PS. modification that you need to do.