策略模式

//接口类
public interface Strategy {
    public int reduce(int pay);
}

//实现1，满五百减两百
public class StrategyA implements Strategy {
    @Override
    public int reduce(int pay) {
        if(pay>500){
            pay-=200;
        }
        return pay;
    }
}

//实现2 满一千打八折
public class StrategyB implements Strategy{
    @Override
    public int reduce(int pay) {
        if(pay>1000){
            pay*=0.8;
        }
        return pay;
    }
}

//实现3 原价
public class StrategyC implements Strategy{
    @Override
    public int reduce(int pay) {
        return pay;
    }
}


//对某次付款进行促销
public class Context {
     public static void main(String[] args) {
        int pay=1850;
        Strategy s1=new StrategyA();
        Strategy s2=new StrategyB();
        Strategy s3=new StrategyC();
        pay=s2.reduce(pay);
        pay=s1.reduce(pay);
        pay=s3.reduce(pay);
        System.out.println(pay);
        
    }
}