code: private void moveToNext(final int i) {
      final HistogramSeekableView it = iterators[i];
      if (it.hasNext()) {
        putDataPoint(i, it.next());
      } else {
        endReached(i);
      }
    }
docs: Makes iterator number {@code i} move forward to the next data point.
  
  @param i The index in {@link #iterators} of the iterator.