@GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;
  }

  abstract static class AbstractCell<
          R extends @Nullable Object, C extends @Nullable Object, V extends @Nullable Object>
      implements Cell<R, C, V> {
    // needed for serialization
    AbstractCell() {}

    @Override
    public boolean equals(@Nullable Object obj) {
      if (obj == this) {
        return true;

        size(), Spliterator.ORDERED | Spliterator.NONNULL | Spliterator.DISTINCT, this::getCell);
  }

  private Cell<R, C, @Nullable V> getCell(int index) {
    return new Tables.AbstractCell<R, C, @Nullable V>() {
      final int rowIndex = index / columnList.size();
      final int columnIndex = index % columnList.size();

      @Override
      public R getRowKey() {

      @Override
      protected Cell<R, C, @Nullable V> get(int index) {
        return getCell(index);
      }
    };
  }

  private Cell<R, C, @Nullable V> getCell(int index) {
    return new Tables.AbstractCell<R, C, @Nullable V>() {
      final int rowIndex = index / columnList.size();
      final int columnIndex = index % columnList.size();

      @Override
      public R getRowKey() {