计策模式 [取自wikipedia]

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 strategy
interface Strategy {
 
    void execute();
 
}
 
// Implements the algorithm using the strategy interface
class 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 object
class Context {
 
    Strategy strategy;
 
    // Constructor
    public Context(Strategy strategy) {
        this.strategy = strategy;
    }
 
    public void execute() {
        this.strategy.execute();
    }
 
}