个人银行账户管理系统（c++改写java）第4章：类

public class SavingsAccount {
    private int id;                 //账号
    private double balance;         //余额
    private double rate;            //存款的年利率
    private int lastDate;           //上次变更余额的时期
    private double accumulation;    //余额按日累加之和
      
    //记录一笔帐，date为日期，amount为金额，desc为说明
    private 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
    private double accumulate(int date)
    { 
        return accumulation + balance * (date - lastDate);
    }
      
    //构造函数及相关成员函数的实现
    public 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");
    }
    public final int getId() { return id; }
    public double getBalance() { return balance; }
    public double getRate() { return rate; }
      
    //存入现金
    public void deposit(int date, double amount)
    {
        if(amount < 0.0){
            System.out.println("Deposit is error!");
            record(date, 0);
        }
        else record(date, amount);
    }
    
    //取出现金
    public void withdraw(int date, double amount)
    {
        if(amount < 0.0){
            System.out.println("Withdraw is error!");
            record(date, 0);
        }
        else 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
    public 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
    public 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();
    sa1.show();
    }
}

 

c++与java的异同：

1.private,public等在java里面需要单独写在每一个成员前面；

2.java不允许普通函数（除抽象类，接口等）的声明与函数体分开，要写在一起；

3.c++的各种头文件在java中存放在类库，在书写代码时不需要表示出来。