public String toString() {
    StringBuilder builder = new StringBuilder().append(super.toString()).append("[status=");
    if (isCancelled()) {
      builder.append("CANCELLED");
    } else if (isDone()) {
      addDoneString(builder);
    } else {
      String pendingDescription;
      try {
        pendingDescription = pendingToString();
      } catch (RuntimeException e) {

    if (isCancelled()) {
      builder.append("CANCELLED");
    } else if (isDone()) {
      addDoneString(builder);
    } else {
      addPendingString(builder); // delegates to addDoneString if future completes midway
    }
    return builder.append("]").toString();
  }

  /**