protected static void incrementValue(Map<Long, Integer> counters, Long toAdd) {
        Integer currValue = counters.get(toAdd);
        if (currValue == null)
            counters.put(toAdd, 1);
        else
            counters.put(toAdd, currValue+1);
    }

    static List sortByValue(Map map) {
        List list = new LinkedList(map.entrySet());
        Collections.sort(list, new Comparator() {
             public int compare(Object o1, Object o2) {
                  return ((Comparable) ((Map.Entry) (o1)).getValue()).compareTo(((Map.Entry) (o2)).getValue());
             }
        });

       Map result = new LinkedHashMap();
       for (Iterator it = list.iterator(); it.hasNext();) {
           Map.Entry entry = (Map.Entry)it.next();
           result.put(entry.getKey(), entry.getValue());
       }
       Collections.reverse(list);
       return list;
   }