Object readResolve() {
      ImmutableMultiset.Builder<Object> builder =
          new ImmutableMultiset.Builder<Object>(elements.length);
      for (int i = 0; i < elements.length; i++) {
        builder.addCopies(elements[i], counts[i]);
      }
      return builder.build();
    }

    private static final long serialVersionUID = 0;
  }

  @Override
  @J2ktIncompatible // serialization