public static void update(List<Block> blocks, List<BlockDTO> blockDTOs) {
       /* REMIND[2017-06-13][Marcus Lin]
        * 更新 blocks
        * 1. 首先判断 blockDTOs 它们的 id 是否全为空，是的话说明原有的 blocks 被清空了，这些 blockDTOs 便是新增的条目
        * 2. 若不为空，则将 blocks 和 blockDTOs 进行比对，以 blockDTOs 的顺序为标准，对 blocks 进行更新及排序，
        * 3. 最后，因为以上的排序会导致某几个 blocks 位置变动从而逃过一些判断，故再一次循环，然后移除掉 id 从未匹配到过的 blocks
        */

       if (isIdAllNull(blockDTOs)) {
           blocks.clear();
           blockDTOs.stream()
                   .map(BlockUtil::toEntity)
                   .forEachOrdered(blocks::add);
       } else {
           List<Long> nonNullIds = new ArrayList<>();
           // add new blocks and sort
           blockDTOs.forEach(blockDTO -> {
               if (blockDTO.getSeq() == null) {
                   blocks.add(blockDTOs.indexOf(blockDTO), BlockUtil.toEntity(blockDTO));
               } else {
                   nonNullIds.add(blockDTO.getSeq());
                   int index = blockDTOs.indexOf(blockDTO);
                   for (int i = 0; i < blocks.size(); i++) {
                       if (blocks.get(i).getSeq() != null) {
                           Block block = blocks.get(i);
                           if (block.getSeq().equals(blockDTO.getSeq())) {
                               // 如果恰巧下标相同，直接 update， 否则交换位置
                               if (i == index) {
                                   BlockUtil.mergeToEntity(blockDTO, block);
                                   break;
                               } else {
                                   Block temp = blocks.get(index);
                                   blocks.set(index, block);
                                   BlockUtil.mergeToEntity(blockDTO, blocks.get(index));
                                   blocks.set(i, temp);
                                   break;
                               }
                           }
                       }
                   }
               }
           });
           // finally loop again to remove the block whose id that never matched
           int removeFlag = 0;
           for (int i = 0; i < blocks.size(); i++) {
               if (blocks.get(i).getSeq() != null) {
                   Block block = blocks.get(i);
                   for (Long id : nonNullIds) {
                       if (!block.getSeq().equals(id)) {
                           removeFlag += 1;
                       } else {
                           removeFlag = 0;
                           break;
                       }
                   }
               }
               if (removeFlag == nonNullIds.size()) {
                   blocks.remove(i);
                   removeFlag = 0;
               }
           }
       }

   }

   private static boolean isIdAllNull(List<BlockDTO> blockDTOS) {
       boolean isAllNull = true;
       for (BlockDTO blockDTO : blockDTOS) {
           if (blockDTO.getSeq() != null) {
               isAllNull = false;
               break;
           }
       }
       return isAllNull;
   }