code: private byte[] getDigest(File file, Configuration conf) throws IOException {
      byte[] def = FileUtil.getFileContents(file);
      MessageDigest alg;
      try {
        alg = MessageDigest.getInstance(conf.digestAlgorithm);
      } catch (NoSuchAlgorithmException e) {
        throw new UnexpectedException(e);
      }
      return alg.digest(def);
    }
docs: Gets the digest of the specified class definition.
  @param def The class definition.
  @param conf The application command line options.
  @return The digest of the class definition.