Cannot find JDK classes
Answered
Hello
I can't add JDK 9.0.4 to my project. When i try to add it say this:

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What IntelliJ IDEA version do you use? Does reinstalling the JDK help?
Using 2017.3.4. version and reinstallind dosen'r help
Can't reproduce the problem. Your JDK installation could be damaged or incomplete. In some cases antivirus monitors delete suspicious files from the app installation directory, make sure it's not the case.
See https://youtrack.jetbrains.com/v2/issue/IDEA-181035.
Please try File | Invalidate Caches | Invalidate and Restart.
JDK 8 I can use without any problems.
Done Invalidate and Restart. and now works. Thank you for help
Did you try File | Invalidate Caches?
Yes and it worked
Just ran into the same issue (same with Oracle and OpenJDK). The invalidate also worked for me, but it is quite annoying. Would be good if someone could take a look at that to avoid running into it?
Please see https://youtrack.jetbrains.com/issue/IDEA-35712. At the moment there is no easy way to detect such problems automatically and it's not an easy thing to implement.