code: public String getString(Enum<?> key, String defaultValue)
      {
          if (key == null)
          {
              return defaultValue;
          }
  
          return getString(key.name(), defaultValue);
      }
docs: Equivalent to {@link #getString(String, String)
  getString}{@code (key.name(), defaultValue)}.
  If {@code key} is null, {@code defaultValue} is returned.