Idea does sometimes suffer from convulsions. In this case, you only need to ask Idea to clean up the previous project files and update the index.

This problem also occurred in IDEA today, but it occurred when a new project was compiled for the first time. I searched and couldn’t find the problem. Finally, I thought that the Chinese path might not be recognized, so I copied the project to the full English path and restarted it. Open, compile. Passed.