I am actively working on a fast language server for Java and kotlin.

I’m driving it daily and it’s much faster than IJ for what I need, although it doesn’t provide all the diagnostics that IJ does…

It’s on github.com/pepegar/ktlsp if you’re curious.

To be clear, it’s not supported by a compiler, but rather plain tree sitter syntax parsing. I’m embarking on a bigger project to create a linter (and integrate) without relying on JVM or a compiler at all, but IDK when that’s gonna come.