银行账户管理程序（二）

1、为savingaccount增加一个静态数据成员total来记录各个账户的总金额，相应的静态成员函数getTotal用来对其访问。

2、将getbalance，accumulate这些成员函数改为常成员函数

3、将SavingAccount类从主函数所在的源文件中分开，建立两个新文件account.h和account.cpp，分别存放在SavingAccount类的定义和实现。

//整个程序分为三个部分：account.h是类定义头文件，account.cpp是类实现文件，1.cpp是主函数文件

//account.h
#ifndef__ACCOUNT_H__
#define__ACCOUNT_H__
class SavingAccount{
private:
    int id;             //账户
    double balance;       //余额
    double rate;          //年利率
    int lastdate;         //余额上一次变化的日期
    double accumulation;  //余额按日累加之和
    int accumulate (int date) const; //获得到指定日期位置的存款累计值
    double getbalance () const{return balance;}
    double getrate() const {return rate;}
    static double total;    //所有账户的总金额
    void record(int date,double amount);    //记账
public:
    SavingAccount(int date,int id,double rate);    //构造函数
    static double getTotal(){return total;}
    void deposit(int date,double amount);   //存款
    void withdrawl(int date,double amount);       //取款
    void show();   //显示余额
    void settle(int date);  //结算利息，每年一月一日调用此函数
};
#endif//__ACCOUNT_H__
//account.cpp
#include "account.h"
#include<cmath>
#include<iostream>
using namespace std;
double SavingAccount::total(0);   //给静态成员数据赋值
//类的成员函数的实现
SavingAccount::SavingAccount(int date,int id,double rate):id(id),balance(0),rate(rate),lastdate(date),accumulation(0){
    cout<<"#"<<id<<"is created"<<endl;
}
int SavingAccount::accumulate(int date){
return accumulation+balance*(date-lastdate);
}
void SavingAccount::record(int date,double amount){
    lastdate=date;
    amount=floor(100*amount+0.5)/100;   //floor为向下取整函数，此处可以做到保留两位小数
    balance+=amount;
    cout<<date<<"\t#"<<id<<"\t"<<amount<<"\t"<<balance<<endl;
}
void SavingAccount::deposit(int date,double amount){
    record(date,amount);
}
void SavingAccount::withdrawl(int date, double amount){
    if(amount>balance)
        cout<<"not enough money"<<endl;
    else
        record(date,-amount);
}
void SavingAccount::show(){
    cout<<"#"<<id<<"\tBalance"<<balance<<endl;
}
void SavingAccount::settle(int date){
    double interest=accumulate(date)*rate/365; //计算年息
    if(interest!=0)
        record(date,interest);
    accumulation=0;
}
//1.cpp
#include"account.h"
#include<iostream>
using namespace std;
int main()
{
    SavingAccount s1(0,11111,0.015);
    SavingAccount s2(1,22222,0.015);
    s1.deposit(5,5000);
    s2.deposit(25,10000);
    s1.deposit(45,5500);
    s2.withdrawl(60,11000);
    s1.settle(90);
    s2.settle(90);
    s1.show();
    s2.show();
    cout<<"Total:"<<SavingAccount::getTotal()<<endl;
    return 0;
}

不知道为什么要这么做