IntelliJ IDEA Ultimate 2018.3 thinks my Java 9 Project is a Kotlin Project

Question

I have an IntelliJ project composing several subprojects which are all Java 9 modules. I use Maven as a build system. My project has no \"Facets\". My run configuration look

Answer 1

Try to rebuild the module using Ctrl+Shift+F9 or right click on the module and select "Rebuild " in menu.

Answer 2

Even in 2019.1.3 that error is there .

A solution that always works for me is :

Build menu => Rebuild Project

Tested with JDK 12.0.1

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That should be fixed though by IntelliJ team as soon as possible as more and more Java projects are passing to JDK 11 ++

Answer 3

I fixed this error by disabling Kotlin plugin since I am not using it and the problem is solved

Answer 4

Update your module-info.java file

requires javafx.fxml;
requires javafx.controls;
requires javafx.graphics;
requires javafx.web;

opens sample;

opens sample.controller;

It opens the package (eg. sample) which contains your Launcher file and opens package conatinsyoyr controllers and its corresponding fxml files (eg. sample.controller)

Answer 5

I had the same issue. Here is what worked:

1. On IntellijIDEA go to 'Tools' menu at the top of the application: .
2. Then scroll down to 'Kotlin'.
3. Click 'Configure Kotlin in Project'.

Answer 6

I had the same problem. I worked in a pure Java project managed with Maven. Till some days ago I applied the solution "rebuild" the project, but sometimes the error came back again.

After more investigation, I found that after disable "Enable migration detection" menu, the problem disappears.

I hope this helps.