Solution: Intellij IDEA won't synchronize with file system changes

Normally this isn't an issue. I've been working with IntelliJ for a few years now and never had this problem before. But no matter what I did, the IDE would only present me with an old version of my filesystem whenever the choose location dialog would come up. Then stranger things started to happen... I couldn't create a new project, builds started to fail and classes that existed on the filesystem wouldn't show up in the project. I took me a while to figure out how to get things back on track, even though the solution takes about 2 seconds once you know what to do.

How It Happened

My battery in my laptop has been misreporting the amount of charge that it has left which causes the computer to abruptly halt when the battery reports about a 15% charge remaining. Normally OSX will hibernate when the charge gets too low but the operating system never gets a chance because the battery misreports.

The problem is that one day my computer turned off when I was working within IntelliJ. After swearing a bit, plugging in the charger and turning the machine back on, I got back into IntelliJ and the weirdness started to happen. So at least in the case of OSX, a hard power off while IntelliJ is open seems to cause this problem.

The Solution

The solution is to delete the internal Intellij cache and let the IDE rebuild it. So when IntelliJ is closed, delete the directory at ~/Library/Caches/IntelliJIDEA80. YMMV-- this location is IntelliJ version and operating system dependent.