个人银行账户管理系统C++转Java（第六章）

第六章
1.Java里没有像c++一样的&符号引用，创建对象时一律使用new。
2.Java里是不允许全局变量的，因为这会破坏封装性。
3.Java里的异常退出exit(1)需要调用System.exit(1)。
4.Java里的字符串类型是一个类String。
5.print不输出换行，println才换行。

package ob3;

public class Date {
	//日期类
		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
		
		//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
		public	final int[] DAYS_BEFORE_MONTH =new int[]{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
		public	void show(){
			System.out.println( getYear()+"-"+getMonth()+"-"+getDay());
		}		//输出当前日期
		public Date(int year, int month, int day){
			this.year=year;
			this.month=month;
			this.day=day;
			if (day <= 0 || day > getMaxDay()) {
				System.out.println( "Invalid date: ");
				show();
				System.out.println();
				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++;
			
		}//用年、月、日构造日期
		public	int getYear() { return year; }
		public	int getMonth() { return month; }
		public	int getDay() { return day; }
		public	int getMaxDay(){
			if (isLeapYear() && month == 2)
				return 29;
			else
				return DAYS_BEFORE_MONTH[month]- DAYS_BEFORE_MONTH[month - 1];
		} //获得当月有多少天
		public	boolean isLeapYear()  {	//判断当年是否为闰年
				return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
			}
		
			//计算两个日期之间差多少天	
		public	int distance(Date date) {
				return totalDays - date.totalDays;
			}

}

package ob3;

public class SavingsAccount {
	//储蓄账户类
	   private String id; //账号
	   private double balance;//余额
	   private double rate;//存款的年利率
	   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
	   //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);
	 	}

		//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+ "\n");
	    }
		
			

		//构造函数
		public SavingsAccount(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(date+"\t#"+id+"is created\n");
		}
		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 void error(String msg){
			System.out.println("Error(#"+id+"): "+msg);
			
		}

}

package ob3;

public class Run {
	public static void main(String[] args){
		//建立几个账户
		Date date=new Date(2008,11,1);
		SavingsAccount[] accounts;
		accounts=new SavingsAccount[2];
		int n = accounts.length;  //账户总数
		accounts[0]=new SavingsAccount(date, "S3755217", 0.015);
		accounts[1]=new SavingsAccount(date, "02342342", 0.015);
		
		//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), 4000, "buy a laptop");
       //结算所有账户并输出各个账户信息
		System.out.println();
		for (int i = 0; i < n; i++) {
			accounts[i].settle(new Date(2009, 1, 1));
			accounts[i].show();
			System.out.println();
		}
		System.out.println("Total: " + SavingsAccount.getTotal());
		
}

}