Under the target folder in IntelliJ for a Java project I created, I have a few java source files in the package. Beside each file the 'J' icon has a red circle with a line through it.
What does that mean? How do I fix it?
You need to specify the source dir
File> Project Structure > Modules
click the directory and click the Sources button
It's weird because usually it's done automatically. Maybe it's better if you recreate the project again.