private void findFollowers(){
        for(int docId = 0; docId<FREE_DOC_ID; docId++) {
            if(!leaders.contains(docId)) {
                TreeMap<Integer, Double> listOfCosSimilarities = new TreeMap<>();
                for(int leader:leaders ) {
                    listOfCosSimilarities.put(leader, findCosSimBetween2Docs(docId, leader));
                }
                LinkedHashMap<Integer, Double> newlistOfCosSimilarities = 
                        (LinkedHashMap)sortByComparator(listOfCosSimilarities);
                Set<Integer> set = newlistOfCosSimilarities.keySet();
                    Object [] keys  = set.toArray();
                    ArrayList<Integer> lst = new ArrayList<>();
                for(int i = 0; i< B1; i++) {
                    lst.add((Integer)keys[i]);
                } 
                followers.put(docId, lst);
            }
        }
    }