个人银行账户管理系统C++转Java（七—九）

4. 个人银行管理系统版本0.4（对应第7章记录）
   这个版本相较于以前的版本，在语法方面没什么明显改变，本版本加入抽象类，来方便实例化两个有些相似的子类，大体方法是和c++一样的，只是一些关键字不太一样。

package PersonalBank4;

public class Date {//日期类
	//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

	public 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.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++;
	}
	public final int getYear() { return year; }
	public final 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());//这里不用println
	}
		//计算两个日期之间差多少天	
	public int distance(final Date date) {
			return totalDays - date.totalDays;
		}

}

package PersonalBank4;

public class Accumulator {//将某个数值按日累加

	private Date lastDate;	//上次变更数值的时期
	private double value;	//数值的当前值
	private double sum;		//数值按日累加之和
	
		//构造函数，date为开始累加的日期，value为初始值
	public Accumulator(final Date date, double value)
	{
		lastDate=date;
		this.value=value;
		sum=0;
	}
		//获得到日期date的累加结果
	public double getSum(final Date date){
			return sum + value * date.distance(lastDate);
		}

		//在date将数值变更为value
	public void change(final Date date, double value) {
			sum = getSum(date);
			lastDate = date;
			this.value = value;
		}

		//初始化，将日期变为date，数值变为value，累加器清零
	public void reset(final  Date date, double value) {
			lastDate = date;
			this.value = value;
			sum = 0;
		}
}

package PersonalBank4;

public class Account {//账户类

	private String id;	//帐号
	private double balance;	//余额
	private static double total = 0; //所有账户的总金额
	
		//供派生类调用的构造函数，id为账户
	protected Account(final Date date, final String id)
	{
		this.id=id;
		balance=0;
		date.show();
		System.out.println("\t#" + id + " created");
	}
		//记录一笔帐，date为日期，amount为金额，desc为说明
	protected void record(final Date date, double amount, final String desc)
	{
		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
	protected void error(final String msg)
	{
		System.out.println("Error(#" + id + "):" + msg);
	}
	
	public final String getId() { return id; }
	public double getBalance() { return balance; }
	public static double getTotal() { return total; }
		//显示账户信息
	public void show()
	{
		System.out.print(id + "\tBalance: " + balance);//这里不用println
	}
}

package PersonalBank4;

public class SavingsAccount extends Account {//储蓄账户类

	private Accumulator acc;	//辅助计算利息的累加器
	private double rate;		//存款的年利率
	
		//构造函数
	public SavingsAccount(final Date date,final String id, double rate)
	{
		super(date,id);
		this.rate = rate;
		acc=new Accumulator(date,0);
	}
	public double getRate() { return rate; }
		//存入现金
	public void deposit(final Date date, double amount,final String desc)
	{
		record(date, amount, desc);
		acc.change(date, getBalance());
	}
		//取出现金
	public void withdraw(final Date date, double amount,final String desc)
	{
		if (amount > getBalance()) {
			error("not enough money");
		} else {
			record(date, -amount, desc);
			acc.change(date, getBalance());
		}
	}
		//结算利息，每年1月1日调用一次该函数
	public void settle(final Date date)
	{
		double interest = acc.getSum(date) * rate / date.distance(new Date(date.getYear() - 1, 1, 1));	//计算年息
		if (interest != 0)
			record(date, interest, "interest");
		acc.reset(date, getBalance());
	}
}

package PersonalBank4;

public class CreditAccount extends Account{//信用账户类

	private Accumulator acc;	//辅助计算利息的累加器
	private double credit;		//信用额度
	private double rate;		//欠款的日利率
	private double fee;			//信用卡年费

	private double getDebt() {	//获得欠款额
			double balance = getBalance();
			return (balance < 0 ? balance : 0);
	}
	
		//构造函数
	public CreditAccount(final Date date,final String id, double credit, double rate, double fee)
	{
		super(date, id);
		this.credit=credit;
		this.rate=rate;
		this.fee=fee;
		acc = new Accumulator(date, 0);
		
	}
	public double getCredit() { return credit; }
	public double getRate() { return rate; }
	public double getFee() { return fee; }
	public double getAvailableCredit() {	//获得可用信用
			if (getBalance() < 0) 
				return credit + getBalance();
			else
				return credit;
		}
		//存入现金
	public void deposit(final Date date, double amount,final String desc)
	{
		record(date, amount, desc);
		acc.change(date, getDebt());
	}
		//取出现金
	public void withdraw(final Date date, double amount,final String desc)
	{
		if (amount - getBalance() > credit) {
			error("not enough credit");
		} else {
			record(date, -amount, desc);
			acc.change(date, getDebt());
		}
	}
		//结算利息和年费，每月1日调用一次该函数
	public void settle(final Date date)
	{
		double interest = acc.getSum(date) * rate;
		if (interest != 0)
			record(date, interest, "interest");
		if (date.getMonth() == 1)
			record(date, -fee, "annual fee");
		acc.reset(date, getDebt());
	}
	public void show()
	{
		super.show();
		System.out.println( "\tAvailable credit:" + getAvailableCredit());
	}
}

package PersonalBank4;
//7_10.cpp
public class PersonalBank {

	public static void main(String[] args) {
		Date date = new Date(2008, 11, 1);	//起始日期
		//建立几个账户
		//SavingsAccount sa1 = new SavingsAccount(date, "AAAAA", 0.015);
		//sa1.deposit(new Date(2008, 11, 5), 5000, "salary");
		//sa1.withdraw(new Date(2008, 12, 5), 500, "happy");
		//sa1.settle(new Date(2009, 1, 1));
		//System.out.println();
		//sa1.show(); System.out.println();
		//System.out.println();
		SavingsAccount sa2 = new SavingsAccount(date, "02342342", 0.015);
		CreditAccount ca = new CreditAccount(date, "BBBBB", 10000, 0.0005, 50);
		//11月份的几笔账目
		
		ca.withdraw(new Date(2008, 11, 15), 2000, "buy a cell");
		sa2.deposit(new Date(2008, 11, 25), 10000, "sell stock 0323");
		//结算信用卡
		//ca.show();
		//ca.withdraw(new Date(2008, 12, 1), 52000, "buy a car");
		//ca.settle(new Date(2008, 12, 30));
		//ca.settle(new Date(2008, 12, 31));
		//ca.settle(new Date(2009, 1, 1));
		//12月份的几笔账目
		//ca.show();
		//ca.deposit(new Date(2008, 12, 31), 2016, "repay the credit");
		
		//结算所有账户
		
		//sa2.settle(new Date(2009, 1, 1));
		//ca.settle(new Date(2009, 1, 1));
		//输出各个账户信息
		//System.out.println();
		
		sa2.show(); System.out.println();
		ca.show();
		System.out.println();
		System.out.println( "Total: " + Account.getTotal());
	}
}

5. 个人银行管理系统版本0.5（对应第8章记录）
   1）在改代码过程中对于show函数是否定为虚函数有很大麻烦，因为两种语言格式不一样，最后取消了纯虚函数的设置，不过也加深了对java的理解。
   2）本版本实现类2个很常见的要求：批量操作和统一接口，因为对象类型不一样，还要求统一实现，就用到虚函数，而函数接口设置为一样，在函数体额外加判断条件，来达到接口统一，更利于程序的封装性，安全性。
   3）java里面的输入输出很有趣，也是调用类库，比如java.text.DecimalFormat可以控制输出小数点，java.io.IOException和java.util.*则是输入的专用库，每种类型的输入还不一样，真的很方便啊！
   Date类和Accumulator类和之前一样，CreditAccount只有show函数不太一样。

package PersonalBank5;

import java.text.DecimalFormat;

abstract public class Account {//账户类

	private String id;	//帐号
	private double balance;	//余额
	private static double total = 0; //所有账户的总金额
	
		//供派生类调用的构造函数，id为账户
	protected Account(final Date date, final String id)
	{
		this.id=id;
		balance=0;
		date.show();
		System.out.println("\t#" + id + " created");
	}
		//记录一笔帐，date为日期，amount为金额，desc为说明
	protected void record(final Date date, double amount, final String desc)
	{
		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" + df.format(balance) + "\t" + desc );
	}
		//报告错误信息
	protected void error(final String msg)
	{
		System.out.println("Error(#" + id + "):" + msg);
	}
	static DecimalFormat df = new DecimalFormat("0.0");
	public final String getId() { return id; }
	public double getBalance() { return balance; }
	public static double getTotal() { return total; }
		//存入现金，date为日期，amount为金额，desc为款项说明
	abstract void deposit(final Date date, double amount,final String desc);
		//取出现金，date为日期，amount为金额，desc为款项说明
	abstract void withdraw(final Date date, double amount,final String desc);
		//结算（计算利息、年费等），每月结算一次，date为结算日期
	abstract void settle(final Date date);
		//显示账户信息
	public void show(){
		System.out.print(id + "\tBalance: " + df.format(balance));
		}
}

package PersonalBank5;

public class SavingsAccount extends Account {//储蓄账户类

	private Accumulator acc;	//辅助计算利息的累加器
	private double rate;		//存款的年利率
	
		//构造函数
	public SavingsAccount(final Date date,final String id, double rate)
	{
		super(date,id);
		this.rate = rate;
		acc=new Accumulator(date,0);
	}
	public double getRate() { return rate; }
		//存入现金
	public void deposit(final Date date, double amount,final String desc)
	{
		record(date, amount, desc);
		acc.change(date, getBalance());
	}
		//取出现金
	public void withdraw(final Date date, double amount,final String desc)
	{
		if (amount > getBalance()) {
			error("not enough money");
		} else {
			record(date, -amount, desc);
			acc.change(date, getBalance());
		}
	}
		//结算利息，每年1月1日调用一次该函数
	public void settle(final Date date)
	{
		if(date.getMonth() == 1) {
			double interest = acc.getSum(date) * rate / date.distance(new Date(date.getYear() - 1, 1, 1));	//计算年息
			if (interest != 0)
				record(date, interest, "interest");
			acc.reset(date, getBalance());
		}
	}
}

CreditAccount:
public void show()
	{
		super.show();
		System.out.print( "\t\tAvailable credit:" + getAvailableCredit());
	}

package PersonalBank5;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.*; 
//8_8.cpp
public class PersonalBank {

	public static void main(String[] args) throws IOException {
		Date date = new Date(2008, 11, 1);	//起始日期
		//建立几个账户
		SavingsAccount sa1 = new SavingsAccount(date, "S3755217", 0.015);
		SavingsAccount sa2 = new SavingsAccount(date, "02342342", 0.015);
		CreditAccount ca = new CreditAccount(date, "C5392394", 10000, 0.0005, 50);
		Account accounts[] = { sa1, sa2, ca };
		final int n = accounts.length;	//账户总数

		System.out.println("(d)deposit (w)withdraw (s)show (c)change day (n)next month (e)exit");
		char cmd;
		Scanner in=new Scanner(System.in); //使用Scanner类定义对象
		int index, day;
		double amount;
		String desc;
		DecimalFormat df = new DecimalFormat("0.0");
		do {
			//显示日期和总金额
			date.show();
			System.out.print("\tTotal: " + df.format(Account.getTotal()) + "\tcommand> ");

			cmd = (char)System.in.read();
			switch (cmd) {
			case 'd':	//存入现金
				index = in.nextInt();
				amount = in.nextDouble();
				desc = in.nextLine();
				accounts[index].deposit(date, amount, desc);
				break;
			case 'w':	//取出现金
				index = in.nextInt();
				amount = in.nextDouble();
				desc = in.nextLine();
				accounts[index].withdraw(date, amount, desc);
				break;
			case 's':	//查询各账户信息
				for (int i = 0; i < n; i++) {
					System.out.print("[" + i + "] ");
					accounts[i].show();
					System.out.println();
					if(i<(n-1)) {System.in.read();}
				}
				break;
			case 'c':	//改变日期
				day = in.nextInt();
				if (day < date.getDay())
					System.out.print("You cannot specify a previous day");
				else if (day > date.getMaxDay())
					System.out.print("Invalid day");
				else
					date = new Date(date.getYear(), date.getMonth(), day);
				break;
			case 'n':	//进入下个月
				if (date.getMonth() == 12)
					date = new Date(date.getYear() + 1, 1, 1);
				else
					date = new Date(date.getYear(), date.getMonth() + 1, 1);
				for (int i = 0; i < n; i++) {
					accounts[i].settle(date);
					if(i<(n-1)) {System.in.read();}
				}
				break;
			}
		} while (cmd != 'e');
		in.close();
	}
}

6. 个人银行管理系统版本0.6（对应第9章记录）
   1）先说些两种程序的不同点。C++里面有动态数组模板Array，可以动态添加对象，java里面有ArrayList，对于这个一开始真的很烦，要去不停的查询，因为他是类库里的东西。各种方法都有。只是我不会用罢了，所以这次的改编基本都在查资料。不过ArrayList确实很方便使用。
   只有主函数和上一版本不一样，其他的类一模一样

package PersonalBank6;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.*; 
//9_16.cpp
public class PersonalBank {

	public static void main(String[] args) throws IOException {
		Date date = new Date(2008, 11, 1);	//起始日期
		ArrayList<Account> accounts = new ArrayList<Account>(0);//创建账户数组，元素个数为0
		//使用Account来构造ArrayList
		DecimalFormat df = new DecimalFormat("0.0");
		System.out.println("(d)deposit (w)withdraw (s)show (c)change day (n)next month (e)exit");
		char cmd;
		Scanner in=new Scanner(System.in); //使用Scanner类定义对象
		do {
			//显示日期和总金额
			date.show();
			System.out.print("\tTotal: " + df.format(Account.getTotal()) + "\tcommand> ");
			char type;
			int index, day;
			double amount,credit,rate,fee;
			String id,desc;
			Account account;
			
			cmd = (char)System.in.read();
			if(cmd != 'a' && cmd != 'd' && cmd != 'w' && cmd != 's' && cmd != 'c' && cmd != 'n' && cmd != 'e')break;
			switch (cmd) {
			case 'a':	//增加账户
				System.in.read();
				type = (char)System.in.read();
				id = in.next();
				if (type == 's') {
					rate = in.nextDouble();
					account = new SavingsAccount(date, id, rate);
				} else {
					credit = in.nextDouble();
					rate = in.nextDouble();
					fee = in.nextDouble();
					account = new CreditAccount(date, id, credit, rate, fee);
				}
				accounts.add(account);//添加元素到表尾
				accounts.trimToSize();//去掉系统多申请的空间
				break;
			case 'd':	//存入现金
				index = in.nextInt();
				amount = in.nextDouble();
				desc = in.nextLine();
				accounts.get(index).deposit(date, amount, desc);//accounts.get()返回下标为该数的存的值，所以返回的就是一个Account类
				break;
			case 'w':	//取出现金
				index = in.nextInt();
				amount = in.nextDouble();
				desc = in.nextLine();
				accounts.get(index).withdraw(date, amount, desc);
				break;
			case 's':	//查询各账户信息
				for (int i = 0; i < accounts.size(); i++) {//size方法返回大小
					System.out.print("[" + i + "] ");
					accounts.get(i).show();
					System.out.println();
					if(i<(accounts.size()-1)) {System.in.read();}
				}
				break;
			case 'c':	//改变日期
				day = in.nextInt();
				if (day < date.getDay())
					System.out.println("You cannot specify a previous day");
				else if (day > date.getMaxDay())
					System.out.println("Invalid day");
				else
					date = new Date(date.getYear(), date.getMonth(), day);
				break;
			case 'n':	//进入下个月
				if (date.getMonth() == 12)
					date = new Date(date.getYear() + 1, 1, 1);
				else
					date = new Date(date.getYear(), date.getMonth() + 1, 1);
				for (int i = 0; i < accounts.size(); i++) {
					accounts.get(i).settle(date);
					if(i<(accounts.size()-1)) {System.in.read();}
				}
				break;
			}
		} while (cmd != 'e');
		System.out.println("Closed!");
		in.close();
		for (int i = 0; i < accounts.size(); i++)
			accounts.remove(i);//删除指定位置的元素
	}
}