@Override
    public String toString() {
      if (!hasData) {
        if (stamp == NULL_STAMP) {
          return "GistData[<none>]";
        }
        else {
          return "GistData[<outdated>, stamp: " + stamp + "]";
        }
      }
      else {
        return "GistData[data: " + data + ", stamp: " + stamp + ']';
      }
    }
@Override
    public String toString()