@Override
      protected @Nullable Integer computeNext(Integer previous) {
        return (previous == last) ? null : previous * 2;
      }
    };
  }

  private static class EmptyAbstractSequentialIterator<T> extends AbstractSequentialIterator<T> {

    EmptyAbstractSequentialIterator() {
      super(null);
    }

    @Override
    protected T computeNext(T previous) {
      throw new AssertionFailedError();

    // second, then signals that it's reached the end of the data
    Iterator<Integer> iter =
        new AbstractIterator<Integer>() {
          private int rep;

          @Override
          public @Nullable Integer computeNext() {
            switch (rep++) {
              case 0:
                return 0;
              case 1:
                return 1;
              case 2:
                return endOfData();
              default:

                  .values()
                  .iterator();
        }
      }
      return new AbstractIterator<Entry<Cut<C>, Range<C>>>() {
        @Override
        protected @Nullable Entry<Cut<C>, Range<C>> computeNext() {
          if (!backingItr.hasNext()) {
            return endOfData();
          }
          Range<C> range = backingItr.next();
          if (upperBoundWindow.upperBound.isLessThan(range.upperBound)) {

  }

  @Override
  public UnmodifiableIterator<C> iterator() {
    return new AbstractSequentialIterator<C>(first()) {
      final C last = last();

      @Override
      protected @Nullable C computeNext(C previous) {
        return equalsOrThrow(previous, last) ? null : domain.next(previous);
      }
    };
  }

  @GwtIncompatible // NavigableSet
  @Override

                  .values()
                  .iterator();
          return new AbstractIterator<Entry<Range<K>, V>>() {

            @Override
            protected @Nullable Entry<Range<K>, V> computeNext() {
              if (backingItr.hasNext()) {
                RangeMapEntry<K, V> entry = backingItr.next();
                if (entry.getUpperBound().compareTo(subRange.lowerBound) <= 0) {

      return new AbstractIterator<C>() {
        final Iterator<Range<C>> rangeItr = ranges.iterator();
        Iterator<C> elemItr = emptyIterator();

        @Override
        protected @Nullable C computeNext() {
          while (!elemItr.hasNext()) {
            if (rangeItr.hasNext()) {
              elemItr = ContiguousSet.create(rangeItr.next(), domain).iterator();
            } else {
              return endOfData();

          final Iterator<? extends E> itr1 = set1.iterator();
          final Iterator<? extends E> itr2 = set2.iterator();

          @Override
          protected @Nullable E computeNext() {
            if (itr1.hasNext()) {
              return itr1.next();
            }
            while (itr2.hasNext()) {
              E e = itr2.next();
              if (!set1.contains(e)) {

            final Iterator<Entry<K, Collection<V>>> backingIterator =
                unfiltered.asMap().entrySet().iterator();

            @Override
            protected @Nullable Entry<K, Collection<V>> computeNext() {
              while (backingIterator.hasNext()) {
                Entry<K, Collection<V>> entry = backingIterator.next();
                K key = entry.getKey();
                Collection<V> collection =

            final Iterator<Entry<K, Collection<V>>> backingIterator =
                unfiltered.asMap().entrySet().iterator();

            @Override
            protected @Nullable Entry<K, Collection<V>> computeNext() {
              while (backingIterator.hasNext()) {
                Entry<K, Collection<V>> entry = backingIterator.next();
                K key = entry.getKey();
                Collection<V> collection =

    private final class EntrySetIterator extends AbstractIterator<Entry<R, V>> {
      final Iterator<Entry<R, Map<C, V>>> iterator = backingMap.entrySet().iterator();

      @Override
      protected @Nullable Entry<R, V> computeNext() {
        while (iterator.hasNext()) {
          Entry<R, Map<C, V>> entry = iterator.next();
          if (entry.getValue().containsKey(columnKey)) {
            @WeakOuter