private static @NotNull FileType getFileType(@Nullable String preferredName) {
    if (preferredName != null) {
      int extOffset = preferredName.lastIndexOf(".");
      if (extOffset >= 0 && preferredName.length() > extOffset + 1) {
        String extension = preferredName.substring(extOffset + 1);
        FileType fileType = FileTypeManager.getInstance().getFileTypeByExtension(extension);
        if (!(fileType instanceof UnknownFileType || fileType.isBinary())) {
          return fileType;
        }
      }
    }
    return PlainTextFileType.INSTANCE;
  }
private static @NotNull FileType getFileType(@Nullable String preferredName)