Harald#eclipse_jdtls can be a real pita
!MESSAGE file:///[clipped]/Groups.java does not resolve to a ICompilationUnit
In 2019: "After cleaning the language server workspace,..."
Yeah, clear the workspace early and often.
Probably: My .classpath was wrecked. I fixed it in the project directory, but, hey, the language server seems to prefer to use some shit cache, even through multiple restarts.
I know it is maintained by volunteers, but 😩 .
https://github.com/redhat-developer/vscode-java/issues/667#issuecomment-500679147
