code: private void convertList(List<?> val){
          if(paths.size() <= 0){
              paths.add("[]");
          }else{
              paths.addLast(paths.removeLast() + "[]");
          }
          for(int i = 0; i < val.size(); i++){
              arrayIndex.addLast(i);
              each(val.get(i));
              arrayIndex.removeLast();
          }
      }
docs: 转换LIST
  @param val