Enabling IntelliSense for Java files in Lua project

I've got a project consisting out of Lua files (using the EmmyLua plugin), basically just a directory opened in IntelliJ IDEA Community Edition. I now have created a Java file (to take advantage of Java's libraries, I want to execute the Java class from Lua (for loading a texture)). Problem is : The Java file doesn't get IntelliSense or anything except for syntax highlighting. It doesn't even look for syntax errors. Auto imports etc don't work, too. How can I enable IntelliSense, Code Completion and all the other nice IntelliJ features for this Java file ?

I have set up a module and am able to run the Java file. But no IntelliSense.

Any help is greatly appreciated.