某大型购物中心欲开发一套收银软件，要求其能够支持购物中心在不同时期推出的各种促销活动，如打折、返利(例如，满300返100),等等。现采用策略(Strategy)模式实现该要求，得到如图7.13 所示的类图。

【Java 代码】

import java.util.*;
enum TYPE { NORMAL,CASH_DISCOUNT,CASH_RETURN};
interface Cashsuper {
    public double acceptCash(double money);
}
class CashNormal implements CashSuper{// 正常收费子类
    public double accptCash(double money){
        return money;
    }
}
class CashDiscount implements Cashsuper {
    private double moneyDiscount;    //折扣率
    public CashDiscount(double moneyDiscount){
        this moneyDiscount = moneyDiscount;
    }
    public double acceptCash(double money){
        return money* moneyDiscount;
    }
}
class CashReturn implements Cashsuper {  //满额返利
    private double moneyCondition;
    private double moneyReturn;
    public CashReturn(double moneyCondition, double moneyReturn){
        this.moneycondition =moneyCondition;//满额数额
        this.moneyReturn =moneyReturn;//返利数额
    }
    public double acceptCash(double money){
        double result = money;
        if (money >= moneyCondition )
            result=money-Math.floor(money/moneyCondition )* moneyReturn;
        return result;
    }
}
class CashContext_{
    private Cashsuper cs;
    private TYPE t;
    public CashContext(TYPE t){
        switch(t){
            case NORMAL;// 正常收费
                cs= new CashNormal();
                break;
            case CASH RETURN;//满300返100
                cs = new CashReturn(300,100);
                break;
            case CASH_ DISCOUNT;//打8折
                cs =new CashDiscount(0.8);
                break;
        }
    }
    public double GetResult(double money){
        return cs.acceptCash(money);
    }
    //此处略去main()函数
}