With 1, the abstraction tends to become "sparse", in the sense that the new thing added to the abstraction will be done only to allow one specific feature to be used.
Yeah, every type can decide how to do it and you can produce new objects or you can modify an existing object in place.，详情可参考体育直播
，这一点在同城约会中也有详细论述
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再叠加 Reddit 的投票排序机制（高赞靠前）和楼中楼对质，它等于把同一问题的多种答案做了一个粗糙但有效的群体筛选。