How to avoid VS Code warning: “[myfile].java is a non-project file, only syntax errors are reported”

Question

I am running a build task in a java project in Visual Studio Code. The warning in the "PROBLEMS" tab:

[myfile].java is a non-project file, only

Answer 1

I got the same warning as well. It was simply because I had two Java projects in the same vscode workspace. Once I've moved projA out of the workspace, the warning for projB is gone.

WorkspaceRoot
│   projectA
└───projectB

At this point, I think the most likely solution is to have one Java (Maven) project for one workspace. Otherwise I guess vscode will treat they all as one project and they'll interfere with each other.