个人银行账户管理系统（c++改写java）第6章：增添字符串、对象数组

public class Account {
    private String id;        //帐号
    private double balance;        //余额
    private double rate;        //存款的年利率
    private date lastDate;        //上次变更余额的时期
    private double accumulation;    //余额按日累加之和
    private static double total = 0;    //所有账户的总金额

        //记录一笔帐，date为日期，amount为金额，desc为说明
    private void record(date date, double amount, String desc)
    {
        accumulation = accumulate(date);
        lastDate = date;
        amount = Math.floor(amount * 100 + 0.5) / 100;    //保留小数点后两位
        balance += amount;
        total += amount;
        date.show();
        System.out.println("\t#" + id + "\t" + amount + "\t" + balance + "\t" + desc);
    }
        //报告错误信息
    private void error(String msg)
    {
        System.out.println("Error(#" + id + "): " + msg);
    }
        //获得到指定日期为止的存款金额按日累积值
    private double accumulate(date date)
    {
        return accumulation + balance * date.distance(lastDate);
    }
     
        //构造函数
    public Account(date date,String id, double rate)
    {
        this.id = id;
        this.balance = 0;
        this.rate = rate;
        this.lastDate = date;
        this.accumulation = 0;
        date.show();
        System.out.println( "\t#" + id + " created");
    }
    public String getId() { return id; }
    public double getBalance() { return balance; }
    public double getRate() { return rate; }
    public static double getTotal() { return total; }

        //存入现金
    public void deposit(date date, double amount, String desc)
    {
        record(date, amount, desc);
    }
        //取出现金
    public void withdraw(date date, double amount, String desc)
     {
        if (amount > getBalance())
            error("not enough money");
        else
            record(date, -amount, desc);
    }
        //结算利息，每年1月1日调用一次该函数
    public void settle(date date)//计算年息
    {
        double interest = accumulate(date) * rate / date.distance(new date(date.getYear() - 1, 1, 1));
        if (interest != 0)
            record(date, interest, "interest");
        accumulation = 0;
    }
        //显示账户信息
    public void show()
    {
        System.out.println(id + "\tBalance: " + balance);
    }
}

public class date {
    //存储平年中某个月1日之前有多少天，为便于getMaxDay函数的实现，该数组多出一项
        final int DAYS_BEFORE_MONTH[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
        private int year;        //年
        private int month;        //月
        private int day;        //日
        private int totalDays;    //该日期是从公元元年1月1日开始的第几天

        boolean isLeapYear() {    //判断当年是否为闰年
            return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
        }
        public date(int year, int month, int day)    //用年、月、日构造日期
        {
            this.day = day;
            this.month = month;
            this.year = year;
            if (day <= 0 || day > getMaxDay()) {
                System.out.println("Invalid date: ");
                show();
                System.exit(1);
            }
            int years = year - 1;
            totalDays = years * 365 + years / 4 - years / 100 + years / 400 + DAYS_BEFORE_MONTH[month - 1] + day;
            if (isLeapYear() && month > 2) totalDays++;
        }
        public int getYear() { return year; }
        public int getMonth() { return month; }
        public int getDay() { return day; }
        public int getMaxDay()        //获得当月有多少天
        {
            if (isLeapYear() && month == 2)
                return 29;
            else
                return DAYS_BEFORE_MONTH[month]- DAYS_BEFORE_MONTH[month - 1];
        }
            
        public void show()            //输出当前日期
        {
            System.out.print(getYear() + "-" + getMonth() + "-" + getDay());
        }
            //计算两个日期之间差多少天    
        int distance(date date)
        {
            return totalDays - date.totalDays;
        }
}

public class main {
    public static void main(String[] args) {
        date date = new date(2008, 11, 1);    //起始日期
        //建立几个账户
        Account accounts[] = {
            new Account(date, "S3755217", 0.015),
            new Account(date, "02342342", 0.015)
        };
        int n = accounts.length; //账户总数
        //11月份的几笔账目
        accounts[0].deposit(new date(2008, 11, 5), 5000, "salary");
        accounts[1].deposit(new date(2008, 11, 25), 10000, "sell stock 0323");
        //12月份的几笔账目
        accounts[0].deposit(new date(2008, 12, 5), 5500, "salary");
        accounts[1].withdraw(new date(2008, 12, 20), 20000, "buy a laptop");

        //结算所有账户并输出各个账户信息
        for (int i = 0; i < n; i++) {
            accounts[i].settle(new date(2009, 1, 1));
            accounts[i].show();
        }
        System.out.println("Total: " + Account.getTotal());
    }
}

1.Java里的字符串类型是一个类String；

2.Java数组必须先初始化才可以使用，初始化的时候会分配内存；动态初始化和静态初始化不能同时存在。