// We serialize by default to ImmutableList, the simplest thing that works.
    return new ImmutableList.SerializedForm(toArray());
  }

  @J2ktIncompatible // serialization
  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  /**
   * Abstract base class for builders of {@link ImmutableCollection} types.
   *
   * @since 10.0

    // We serialize by default to ImmutableList, the simplest thing that works.
    return new ImmutableList.SerializedForm(toArray());
  }

  @J2ktIncompatible // serialization
  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  /**
   * Abstract base class for builders of {@link ImmutableCollection} types.
   *
   * @since 10.0