java银行管理4.9

public class SavingsAccount {

int id;				//账号
double balance;		//余额
double rate;		//存款的年利率
int lastDate;		//上次变更余额的时期
double accumulation;	//余额按日累加之和

void record(int date, double amount) {
    accumulation = accumulate(date);
    lastDate = date;
    amount = Math.floor(amount * 100 + 0.5) / 100;	//保留小数点后两位
    balance += amount;
    System.out.println(date+"\t#"+id+"\t"+amount+"\t"+balance);
}

//获得到指定日期为止的存款金额按日累积值
double accumulate(int date)  {
    return accumulation + balance * (date - lastDate);
}

SavingsAccount(int date, int id, double rate) {
    this.id=id;
    this.balance=0;
    this.rate=rate;
    this.lastDate=date;
    this.accumulation=0;
    System.out.println(date+"\t#"+id+" is created");
}

int getId() { return id; }
double getBalance() { return balance; }
double getRate() { return rate; }

//存入现金
void deposit(int date, double amount) {
    record(date, amount);
}

//取出现金
void withdraw(int date, double amount) {
    if (amount > getBalance())
        System.out.println("Error: not enough money");
    else
        record(date, -amount);
}

//结算利息，每年1月1日调用一次该函数
void settle(int date) {
    double interest = accumulate(date) * rate / 365;	//计算年息
    if (interest != 0)
        record(date, interest);
    accumulation = 0;
}

//显示账户信息
void show() {
    System.out.println("#"+id+"\tBalance: "+balance);
}

public static void main(String[] args) {
    //建立几个账户
    SavingsAccount sa0=new SavingsAccount(1, 21325302, 0.015);
    SavingsAccount sa1=new SavingsAccount(1, 58320212, 0.015);

    //几笔账目
    sa0.deposit(5, 5000);
    sa1.deposit(25, 10000);
    sa0.deposit(45, 5500);
    sa1.withdraw(60, 4000);

    //开户后第90天到了银行的计息日，结算所有账户的年息
    sa0.settle(90);
    sa1.settle(90);

    //输出各个账户信息
    sa0.show();
    System.out.println();
    sa1.show();
    System.out.println();
}

}