We can use a pattern called Double Dispatch to pull out the variation into the subclasses in such a way that we don't break existing interface contracts.

我们可以使用称为双重分发的模式将变化推入子类中，通过这种方式，我们不需要破坏现有的接口定义。

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In this condo's living room, a handy pull-out shelf functions as a dining table while a coffee table does double duty as a bench.

这是公寓楼中的一个起居室，一张推拉式的木板既可用作收纳之用，又可作为咖啡桌使用。

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The Azzurri suffered a double blow during the week, when Fabio Grosso was forced to pull out with a thigh strain and Simone Perrotta was also injured during training on Wednesday.

本周国家队遭受了两次打击，格罗索因大腿拉伤缺席，佩罗塔也在周三的训练中受伤。

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