C++ 创建一个SavingAccount类

具体要求：创建一个SavingAccount类。使用一个static数据成员annualnterestRate保存每个存款者目前存款金额。该类提供成员函数calculateMonthlyInterest，它将余额乘以annualInterestRate再除以12来计算月利息，这个利息应该加到savingsBalance中。该类还提供一个static成员函数modifylnterestRate，它将static的annualInterestRate设置为一个值。编写一个驱动程序测试SavingsAccount类。实例化SavingsAccount类的两个对象saverl和saver2,余额分别是$2000.00和$3000.00。将annualInterestRate设置为3%，然后计算月利率并打印每个存款者的新余额。接着再将annualInterestRate设置为4%，计算下一个月的利息并打印每个存款者的新余额。

完整的代码如下：

//创建一个SavingAccount类
#include<iostream>
using namespace std;
class SavingAccount 
{
public:
	SavingAccount(float savingBalance_,float annualInterestRate_)
	{
		savingBalance=savingBalance_;
		annualInterestRate=annualInterestRate_;
	}
	float calculateMonthyInterest()//计算月利息 
	{
		float monthyInterest;
		monthyInterest = savingBalance*annualInterestRate;
		savingBalance += monthyInterest/12;
		return monthyInterest;
	} 
	static void modifyInterestRate(float newAnnualInterestRate)//将annualInterestRate设置为一个新值 
	{
		annualInterestRate = newAnnualInterestRate;
	}
	
private:
	float savingBalance;//用于指示目前的存款余额 
	static float annualInterestRate;//保存每个存款者的年利率 
};

float SavingAccount::annualInterestRate;//static数据成员必须在文件作用域（在类定义体以外）进行定义 

int main()
{
	SavingAccount saver1(2000,0.03);
	float saver1_=saver1.calculateMonthyInterest() ;
	float saver2_=saver1.calculateMonthyInterest() ;
	cout << "saver1 的新余额为 ：" << saver1_ << endl; 
	cout << "saver2 的新余额为 ：" << saver2_ << endl; 
	
	SavingAccount saver2(3000,0.04);
	float saver1__=saver1.calculateMonthyInterest() ;
	float saver2__=saver1.calculateMonthyInterest() ;
	cout <<"下个月的利息为 ：" << saver1__ - saver1_ << " "<<"saver1 的新余额为 ：" << saver1__ << endl; 
	cout <<"下个月的利息为 ：" << saver2__ - saver2_ << " "<<"saver2 的新余额为 ：" << saver2__ << endl;
	return 0;
}