}
                }
                buf.append('}');
                buf.append('\n');
                try {
                    response.getWriter().print(buf.toString());
                } catch (final IOException e) {
                    throw new IORuntimeException(e);
                }
                return true;
            }, OptionalThing.empty());

      state = null;
    }

    @Override
    @CheckForNull
    protected String pendingToString() {
      InCompletionOrderState<T> localState = state;
      if (localState != null) {
        // Don't print the actual array! We don't want inCompletionOrder(list).toString() to have
        // quadratic output.
        return "inputCount=["
            + localState.inputFutures.length
            + "], remaining=["