code: private static String getConfValue(String defaultValue, String keySuffix,
        Configuration conf, String... keys) {
      String value = null;
      for (String key : keys) {
        if (keySuffix != null) {
          key += "." + keySuffix;
        }
        value = conf.get(key);
        if (value != null) {
          break;
        }
      }
      if (value == null) {
        value = defaultValue;
      }
      return value;
    }
docs: Given a list of keys in the order of preference, returns a value
  for the key in the given order from the configuration.
  @param defaultValue default value to return, when key was not found
  @param keySuffix suffix to add to the key, if it is not null
  @param conf Configuration
  @param keys list of keys in the order of preference
  @return value of the key or default if a key was not found in configuration