转载自：https://blog.csdn.net/fightHHA/article/details/81626383
https://blog.csdn.net/weixin_49199646/article/details/109492763?spm=1001.2101.3001.6650.8&utm_medium=distribute.pc_relevant.none-task-blog-2~default~BlogCommendFromBaidu~Rate-8-109492763-blog-119088899.pc_relevant_default&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2~default~BlogCommendFromBaidu~Rate-8-109492763-blog-119088899.pc_relevant_default&utm_relevant_index=9
标签：default,relevant,实现,多态,utm,blog,pc,109492763,原理 From： https://www.cnblogs.com/sound-of-wind-rain/p/16800397.html