private static CSVReader openCsv(File file) throws IOException {

    final Reader fileReader;

    if (file.getName().endsWith(".gz")) {

      final GZIPInputStream inputStream =

          new GZIPInputStream(new FileInputStream(file));

      fileReader = new InputStreamReader(inputStream);

    } else {

      fileReader = new FileReader(file);

    }

    return new CSVReader(fileReader);

  }