策略模式 [取自wikipedia]
策略模式作为一种软件设计模式，指对象有某个行为，但是在不同的场景中，该行为有不同的实现算法。比如每个人都要“交个人所得税”，但是“在美国交个人所得税”和“在中国交个人所得税”就有不同的算税方法。
//StrategyExample test application class StrategyExample { public static void main(String[] args) { Context context; // Three contexts following different strategies context = new Context(new FirstStrategy()); context.execute(); context = new Context(new SecondStrategy()); context.execute(); context = new Context(new ThirdStrategy()); context.execute(); } } // The classes that implement a concrete strategy should implement this // The context class uses this to call the concrete strategyinterface Strategy { void execute(); } // Implements the algorithm using the strategy interfaceclass FirstStrategy implements Strategy { public void execute() { System.out.println("Called FirstStrategy.execute()"); } } class SecondStrategy implements Strategy { public void execute() { System.out.println("Called SecondStrategy.execute()"); } } class ThirdStrategy implements Strategy { public void execute() { System.out.println("Called ThirdStrategy.execute()"); } } // Configured with a ConcreteStrategy object and maintains a reference to a Strategy objectclass Context { Strategy strategy; // Constructor public Context(Strategy strategy) { this.strategy = strategy; } public void execute() { this.strategy.execute(); } }