@Nonnull
  public static String extractPackageName(@Nonnull final String fileNameWithoutExtension) {
    final int lastDot = fileNameWithoutExtension.lastIndexOf('.');
    if (lastDot < 0) {
      return "";
    }
    return fileNameWithoutExtension.substring(0, lastDot).trim();
  }
@ Nonnull public static String extractPackageName ( @ Nonnull final String fileNameWithoutExtension ) { final int lastDot = fileNameWithoutExtension . lastIndexOf ( '.' ) ; if ( lastDot < 0 ) { return "" ; } return fileNameWithoutExtension . substring ( 0 , lastDot ) . trim ( ) ; }
Extract package name from canonical Java class name

@param fileNameWithoutExtension canonical class name (like 'a.b.c.SomeClassName'), must not be null
@return extracted package name, must not be null but can be empty