如何将客户更改为不同的会员？Java的

Question

我正在尝试学习Java中的继承和接口.我有三个不同的类:Customer,SilverCustomer和GoldCustomer.SilverCustomer和GoldCustomer都扩展了客户.

在申请中,客户获得旅行积分.普通客户获得他们前往积分的里程数.SilverCustomer获得里程*1.5,GoldCustomer获得里程*2分.

当我创建一个普通的客户John时,如何使用方法降级()和升级()在普通客户,silvercustomer和goldcustomer之间切换？

class Testfile {
     public static void main(String[] args) {

         Airline aProgram = new Airline();

         Customer john = new Customer("john", 10001); // 10001 is the id number and the status of a customer is normal

         aProgram.addMembers(john);

    john.update_mileage(12000);
    john.upgrade(); //upgrade John to SilverCustomer
    john.update_mileage(2000);

     aProgram.printAllCustomerMilege(); 
   }
}

Answer 1

创建对象后,无法更改对象的类.

如果您的逻辑取决于您的客户类型,则可以使用策略设计模式.在您的示例中,您可以编写如下内容:

interface Strategy {
    double getMileageCoefficient();
}
class NormalCustomerStrategy implements Strategy {
    public double getMileageCoefficient() {
        return 1.0;
    }
}
class GoldCustomerStrategy implements Strategy {
    public double getMileageCoefficient() {
        return 2.0;
    }
}

在您的Customer类中将有一个私有字段Strategy strategy;然后您的升级方法将如下所示:

void upgrade() {
    this.strategy = new GoldCustomerStrategy();
}

而upgradeMileage方法:

void upgradeMileage(double mileage) {
    this.mileage += strategy.getMileageCoefficient() * mileage;
}