Java and Scala ClassNotFoundException after upgrading to IntelliJ 14
问题 I recently upgraded to IntelliJ 14 , then added Scala support. My main files stopped running. For example the GUI file, which has no errors and is a totally self contained hello world style for testing this error: Exception in thread "main" java.lang.ClassNotFoundException: GUI It makes no sense and I'm pretty frustrated that the IntelliJ devs are slacking in not auto-detecting a solution to this. I have tried everything to fix it. From settings, compilers, to making the project from scratch.