https://www.bilibili.com/video/BV1PJ411n7xZ?p=100&spm_id_from=pageDriver
9min
解释的很好的:https://www.zhihu.com/question/435698219/answer/1636587307
https://zhidao.baidu.com/question/443750734.html
https://blog.csdn.net/weixin_38106322/article/details/108760162
https://www.cnblogs.com/itxiaok/p/10356508.html : 我们生成的对象都会有个字段记录该对象所属类在CLass类的对象的所在位置。如下图所示