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) {

    } else if (obj instanceof Failure) {
      throw new ExecutionException(((Failure) obj).exception);
    } else if (obj == NULL) {
      /*
       * It's safe to return null because we would only have stored it in the first place if it were
       * a valid value for V.
       */
      return uncheckedNull();
    } else {