Question for using wrapper class at POJO

Sorry, I don't know where is a suitable place to discuss the question, so I just open an issue here to ask my question.

I have a question about the 8th point of [OOP rules](https://github.com/alibaba/Alibaba-Java-Coding-Guidelines#oop-rules).
> 8. [Mandatory] Rules for using primitive data types and wrapper classes:
  1) Members of a POJO class must be wrapper classes.
  2) The return value and arguments of a RPC method must be wrapper classes.
  3) [Recommended] Local variables should be primitive data types.

Based on this rule, it will only allow us to use the primitive type in local variables. Then, we need to use wrapper classes in all other places.

The thing is that most of the suggestions I saw at the Internet is we should avoid wrapper classes as much as possible.
The reasons are
- performance
- memory footprint

So could anybody explain the reason behind this rule? Thanks. 🙏

从链接的 OOP 规则开始，尤其是规则 8 及其关于 primitive 类型和 wrapper 类型的指导。一个有用的成果是得到 maintainer 批准的规则解释或澄清，但 issue 没有指出要更新的文档文件或测试。

由索引模型根据 Issue 内容生成。