private PostingsList intersect(PostingsList postingsList1, PostingsList postingsList2) {
        PostingsList result = new PostingsList();
        ListIterator<PostingsEntry> p1Iterator = postingsList1.getIterator();
        ListIterator<PostingsEntry> p2Iterator = postingsList2.getIterator();
        PostingsEntry p1 = p1Iterator.next();
        PostingsEntry p2 = p2Iterator.next();
        Boolean start = Boolean.TRUE;
        while( (p1Iterator.hasNext() && p2Iterator.hasNext()) || start) {
            start = Boolean.FALSE;
            if (p1.docID == p2.docID) {
                result.add(p1.docID, 0);
                p1 = p1Iterator.next();
                p2 = p2Iterator.next();
            } else if (p1.docID < p2.docID) {
                p1 = p1Iterator.next();
            } else {
                p2 = p2Iterator.next();
            }
        }

        return result;
    }


    private PostingsList intersect(PostingsList p1, PostingsList p2) {
        PostingsList result = new PostingsList();
        int i = 0;
        int j = 0;
        while (i < p1.size() && j < p2.size()) {
            if(p1.get(i).docID == p2.get(j).docID) {
                result.add(p1.get(i).docID, 0);
                i++;
                j++;
            } if ( p1.get(i).docID < p2.get(j).docID) {
                i++;
            } else {
                j++;
            }
        }
        return result;
    }