Java and Scala ClassNotFoundException after upgrading to IntelliJ 14
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.
I only had a bit of luck when making it from scratch, but as soon as I started to add my other files (files that were not even being used!) it starts with the error.
It seems that any files outside of the original project module (when creating a new project to test fix) will not run giving ClassNotFoundException.
This may be related to my other question: https://stackoverflow.com/questions/27516673/cannot-run-file-located-out-of-main-module-intellij-14-java-scala
Answer
Sample View of the problem
I had the same problem and was able to fix it by right clicking the directory my class was in, and clicking Mark as sources root. This should make your class discoverable and able to run.
Solution
