java设计模式-组合模式详解

public interface DiscountStrategy {
    public double getTotal(double price);
}
public class VIPDiscount implements DiscountStrategy {
    //95折
    @Override
    public double getTotal(double price) {
        return 0.95*price;
    }
}
public class ActivityDiscount implements DiscountStrategy{
    //9折
    @Override
    public double getTotal(double price) {
        return 0.9*price;
    }
}
public class StoreDiscount implements DiscountStrategy{
    //满500超出部分打6折
    @Override
    public double getTotal(double price) {
        return 500+0.6*(price-500);
    }
}

public abstract class CompositeDiscount implements DiscountStrategy {
    protected List<DiscountStrategy> strategies =new ArrayList(); //容器
    public void add(DiscountStrategy discountStrategy){ //添加叶子结点
        strategies.add(discountStrategy);
    }
    @Override
    public double getTotal(double price) {
        return price;
    }
}
//多种折扣选最低折扣
public class SingleMinStrategy extends CompositeDiscount {
    @Override
    public double getTotal(double price) {
        double rtn=price;
        for (DiscountStrategy s: strategies) {
            rtn=Math.min(rtn,s.getTotal(price));
        }
        return rtn;
    }
}
//多种折扣用折上折
public class MultipleStrategy extends CompositeDiscount {
    @Override
    public double getTotal(double price) {
        double rtn = price;
        for (DiscountStrategy s : strategies) {
            rtn = s.getTotal(rtn);
        }
        return rtn;
    }
}

public class DiscountFactory {
    public DiscountStrategy create(String type){ //工厂来创建相应策略
        //单一折扣策略
        if("ynn".equals(type))return new VIPDiscount();
        else if("nyn".equals(type))return new StoreDiscount();
        else if("nny".equals(type))return new ActivityDiscount();
        else{  //多种折扣策略
            CompositeDiscount compositeDiscount;
            System.out.println("请选择冲突解决方案：1.折上折 2.最低折");
            Scanner scanner=new Scanner(System.in);
            int type2=scanner.nextInt();
            if(type2==1){
                compositeDiscount=new MultipleStrategy();
            }
            else{
                compositeDiscount=new SingleMinStrategy();
            }
            if(type.charAt(1)=='y')compositeDiscount.add(new StoreDiscount());
            if(type.charAt(0)=='y')compositeDiscount.add(new VIPDiscount());
            if(type.charAt(2)=='y')compositeDiscount.add(new ActivityDiscount());
            return compositeDiscount;
        }
    }
}

public class Order {
    public double price;
    private String type;
    public DiscountStrategy discountStrategy;
    public Order(double price) {
        this.price=price;
    }
    public void display(){
        System.out.println("总价："+price);
        System.out.println("是否是VIP？y/n");
        Scanner scanner=new Scanner(System.in);
        type=scanner.next();
        System.out.println("是否超过500？y/n");
        String tmp;
        tmp=scanner.next();
        type+=tmp;
        System.out.println("是否满足活动价？y/n");
        tmp=scanner.next();
        type+=tmp;
        DiscountFactory discountFactory=new DiscountFactory();
        double discountPrice=discountFactory.create(type).getTotal(price);
        System.out.println("优惠："+(price-discountPrice));
        System.out.println("应付："+discountPrice);
    }
}
public class Client {
    public static void main(String[] args) {
        Order order=new Order(620);
        order.display();
    }
}