Project idea java error Error: (1, 1) java: Illegal characters: '\ ufeff'

Mainly because of problems UTF-8 and UTF-8 with BOM's

solution:

1. The file encodings into a utf-8 utf-16, then changed utf-16 utf-8 (general procedure)

2. Click on the specified project, right, "Remove BOM" (My IDEA 2018.2 active)

3. If the above methods do not take effect, it can only be modified through Notepad ++ a file encoded as UTF-8 with no BOM of