updateModifyedByAndDate();
updateModifiedByAndDate();
    public ResultDocumentFile addDocumentFile(String filename, String displayName,            FileResultPermittedGroupType permittedGroupType, String mimeType, String checksum,            String checksumAlgorithm, Integer size, String externalStorageId, Group permittedGroup) {        final ResultDocumentFile documentFile = new ResultDocumentFile(this, filename, displayName,                permittedGroupType, mimeType, checksum, checksumAlgorithm, size, externalStorageId,                permittedGroup);        updateModifyedByAndDate();        return documentFile;    }