Intellij stopped detecting .java files

Question

This is the first time something like that happens to me. At some point, Intellij stopped showing .java files. It stil lshows the package structure. But no .java files there. If I try to drag a file from the explorer, It opens it with this message:

// IntelliJ API Decompiler stub source generated from a class file Implementation of methods is not available

When I try to navigate to a class or file (Ctrl+N, Ctrl+Shft+N), nothing pops out. Naturally, the files are there. I tried restarting intellij, restarting the computer, reopening the project (using POM, if it matters). and running around the table a few times. Nothing helps.

Appreciate some input on how to resolve this. Can't seems to find anything like that online..

The project pane looks like this (product name is obfuscated):

Answer 1

Files -> Invalidate caches / Restart worked for me.

Answer 2

Right click on pom.xml select Maven -> Reimport do the trick.