code: public static List<Integer> randomizeWithinLimit(int limit) {
          List<Integer> list = new ArrayList<Integer>(limit);
          for (int i = 0; i < limit; i++) {
              list.add(i);
          }
          Collections.shuffle(list, new Random());
          return list;
      }
docs: 产生[0-limit]之间的一个不重复随机list
  
  @param limit
  
  @return 随机化的list