code: public static List<Integer> randomSerial(int limit) {
          List<Integer> list = new ArrayList<Integer>(limit);
  
          for (int ix = 0; ix < limit; ++ix) {
              list.add(ix);
          }
  
          Collections.shuffle(list, new Random());
          return list;
      }
docs: 获取一堆数据
  
  @param limit
  @return