Idea compile java file error illegal character: '\ufeff'

Problem: Error:(1, 1) java: Illegal character: '\ufeff' Error:(1, 10) java: class, interface or enum is required when compiling the java file in the project with
idea : Copy these error-reported files to a directory, then open them with notpad++, click the encoding on the tool class, convert the encoding in uft8 format to encoding in utf8 format without BOM, save it, and then overwrite the corresponding file in idea.