code: public static JsonParser createJsonParser(CoronaConf conf)
      throws IOException {
      InputStream inputStream = new FileInputStream(conf.getCMStateFile());
      if (conf.getCMCompressStateFlag()) {
        inputStream = new GZIPInputStream(inputStream);
      }
      ObjectMapper mapper = new ObjectMapper();
      mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES,
        false);
      JsonFactory jsonFactory = new JsonFactory();
      jsonFactory.setCodec(mapper);
      return jsonFactory.createJsonParser(inputStream);
    }
docs: This is a helper method which creates a JsonParser instance, for reading
  back the state of the ClusterManager from the state file. The JsonParser
  instance reads from a compressed file if we have the compression flag
  turned on.
  
  @param conf The CoronaConf instance to be used
  @return The JsonParser instance to be used
  @throws IOException