code: @Override
    public int nextStartPosition() throws IOException {
      if (findMatches()) {
        currentMatch = queueMatches.get(0);
        queueMatches.remove(0);
        noMorePositions = false;
        return currentMatch.startPosition();
      } else {
        currentMatch = null;
        noMorePositions = true;
        return NO_MORE_POSITIONS;
      }
    }
docs: /*
  (non-Javadoc)
  
  @see org.apache.lucene.search.spans.Spans#nextStartPosition()