概念

结构

案例代码

定义一个促销活动共同接口

public interface Strategy {
    void show();
}

定义具体策略角色

public class StrategyA implements Strategy{
    @Override
    public void show() {
        System.out.println("买一送一");
    }
}

public class StrategyB implements Strategy{
    @Override
    public void show() {
        System.out.println("满200送50");
    }
}

定义环境角色(context) 联系上下文

public class SaleMan {
    private Strategy strategy;

    public SaleMan(Strategy strategy){
        this.strategy = strategy;
    }

    public void sale(){
        strategy.show();
    }
}

根据传进来的策略对象来实现不同的策略方法

public class Test {
    public static void main(String[] args) {
        StrategyA strategyA = new StrategyA();
        SaleMan saleMan = new SaleMan(strategyA);
        saleMan.sale();
        //切换B策略
        saleMan.setStrategy(new StrategyB());
        saleMan.sale();
    }
}

总结