对策模式-Strategy

策略模式--Strategy


?策略模式的目的是定义一系列算法,把它们封装起来,并且使它们可以相互替换.
本模式使得算法可以独立于它的客户而变话.



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/** ??*?抽象策略（Strategy）角色 ??*?@author?Salmon ??* ??*/??public?interface?Strategy?{ ?? ????public?void?algorithmInterface(); ?? } ????/** ??*?具体策略（ConcreteStrategy）角色 ??*?@author?Salmon ??* ??*/??public?class?ConcreteStrategyA?implements?Strategy?{ ?? ????public?void?algorithmInterface()?{ ?? ????????System.out.println("Called?ConcreteStrategyA.algorithmInterface()"); ?? ????} ??} ????/** ??*?具体策略（ConcreteStrategy）角色 ??*?@author?Salmon ??* ??*/??public?class?ConcreteStrategyB?implements?Strategy?{ ?? ????public?void?algorithmInterface()?{ ?? ????????System.out.println("Called?ConcreteStrategyB.algorithmInterface()"); ?? ????} ??} ????/** ??*?具体策略（ConcreteStrategy）角色 ??*?@author?Salmon ??* ??*/??public?class?ConcreteStrategyC?implements?Strategy?{ ?? ????public?void?algorithmInterface()?{ ?? ????????System.out.println("Called?ConcreteStrategyC.algorithmInterface()"); ?? ????} ??} ????/** ??*?环境（Context）角色 ??*?@author?Salmon ??* ??*/??public?class?Context?{ ?? ????Strategy?strategy; ????????public?Context(Strategy?strategy)?{ ?? ????????this.strategy?=?strategy; ?? ????} ????????public?void?contextInterface()?{ ?? ????????strategy.algorithmInterface(); ??????} ??} ????/** ??*?客户端代码 ??*?@author?Salmon ??*? ??*/??public?class?Client?{ ?? ????public?static?void?Main(String[]?args)?{ ?? ????????Context?c?=?new?Context(new?ConcreteStrategyA()); ?? ????????c.contextInterface(); ????????????Context?d?=?new?Context(new?ConcreteStrategyB()); ?? ????????d.contextInterface(); ????????????Context?e?=?new?Context(new?ConcreteStrategyC()); ?? ????????e.contextInterface(); ??????} ??}?

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应用场合：

1、多个类的分别只是在于行为的不同。

2、你需要对行为的算法做很多的变动。

3、客户不知道算法要使用的数据。