private File getFile(String pid, String dsId, String dsVersionId) {
        File dir = new File(baseDir, getPath(pid));
        String filename = encode(pid, dsId, dsVersionId);
        return new File(dir, filename);
    }
private File getFile ( String pid , String dsId , String dsVersionId ) { File dir = new File ( baseDir , getPath ( pid ) ) ; String filename = encode ( pid , dsId , dsVersionId ) ; return new File ( dir , filename ) ; }
dsId and dsVersionId may be null