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

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

    PostOrderIterator(T root) {
      this.stack = new ArrayDeque<>();
      stack.addLast(expand(root));
    }

    @Override
    @CheckForNull
    protected T computeNext() {
      while (!stack.isEmpty()) {
        PostOrderNode<T> top = stack.getLast();
        if (top.childIterator.hasNext()) {
          T child = top.childIterator.next();
          stack.addLast(expand(child));

                unfiltered.asMap().entrySet().iterator();

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

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

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

                unfiltered.asMap().entrySet().iterator();

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

            comparator);

    return new AbstractIterator<C>() {
      @CheckForNull C lastValue;

      @Override
      @CheckForNull
      protected C computeNext() {
        while (merged.hasNext()) {
          C next = merged.next();
          boolean duplicate = lastValue != null && comparator.compare(next, lastValue) == 0;

          private final Iterator<? extends Optional<? extends T>> iterator =
              checkNotNull(optionals.iterator());

          @Override
          @CheckForNull
          protected T computeNext() {
            while (iterator.hasNext()) {
              Optional<? extends T> optional = iterator.next();
              if (optional.isPresent()) {
                return optional.get();
              }

          private final Iterator<Map.Entry<E, AtomicInteger>> mapEntries =
              countMap.entrySet().iterator();

          @Override
          @CheckForNull
          protected Entry<E> computeNext() {
            while (true) {
              if (!mapEntries.hasNext()) {
                return endOfData();
              }
              Map.Entry<E, AtomicInteger> mapEntry = mapEntries.next();

      return new AbstractIterator<String>() {
        Iterator<String> lines = LINE_SPLITTER.split(seq).iterator();

        @Override
        @CheckForNull
        protected String computeNext() {
          if (lines.hasNext()) {
            String next = lines.next();
            // skip last line if it's empty
            if (lines.hasNext() || !next.isEmpty()) {
              return next;