Spliterator that handles EsIterators.

EsSpliterator.java

class EsSpliterator<T> implements Spliterator<Collection<T>> {
  private final List<EsIterator<T>> iterators = new ArrayList<>();
  // constructor omitted

  private static <T> EsSpliterator<T> from(String index, QueryBuilder query, int batchSize, Class<T> documentClass, int maxSlices) {
      List<EsIterator<T>> iterators = IntStream.range(0, maxSlices)
          .mapToObj(i -> new EsIterator<>(index, query, batchSize, documentClass, i, maxSlices))
          .collect(toList());

      return new EsSpliterator<>(iterators);
  }
  
  @Override
  public boolean tryAdvance(Consumer<? super Collection<T>> action) {
      List<EsIterator<T>> hasNextIterators = iterators.stream()
          .filter(EsIterator::hasNext)
          .collect(toList());

      if (!hasNextIterators.isEmpty()) {
          hasNextIterators.forEach(it -> action.accept(it.next()));
          return true;
      }

      return false;
  }

  @Override
  public Spliterator<Collection<T>> trySplit() {
      if (iterators.size() >= 2) {
          List<EsIterator<T>> sublist = iterators.stream()
              .limit(iterators.size() / 2)
              .collect(toList());

          iterators.removeAll(sublist);
          return new EsSpliterator<>(sublist);
      }

      return null;
  }

  @Override
  public long estimateSize() {
      return iterators.stream().map(EsIterator::getTotalHits).mapToLong(l -> l).sum();
  }

  @Override
  public int characteristics() {
      return SIZED;
  }
}