}

  /** Returns the {@link #sum} as a {@code double} after a widening primitive conversion. */
  @Override
  public double doubleValue() {
    return (double) sum();
  }

  private void writeObject(ObjectOutputStream s) throws IOException {
    s.defaultWriteObject();
    s.writeLong(sum());
  }

  private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {

  }

  /** Returns the {@link #sum} as a {@code double} after a widening primitive conversion. */
  @Override
  public double doubleValue() {
    return (double) sum();
  }

  private void writeObject(ObjectOutputStream s) throws IOException {
    s.defaultWriteObject();
    s.writeLong(sum());
  }

  private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {

  }

  /** Returns the {@link #sum} as a {@code double} after a widening primitive conversion. */
  @Override
  public double doubleValue() {
    return (double) sum();
  }

  private void writeObject(ObjectOutputStream s) throws IOException {
    s.defaultWriteObject();
    s.writeLong(sum());
  }

  private void readObject(ObjectInputStream s) throws IOException, ClassNotFoundException {