Java实验一

1.第四章：类

class SavingsAccount4 { //储蓄账户类
    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
    public SavingsAccount4(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 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){
        record(date, amount);
    }
    //取出现金
    public 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
    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){
        SavingsAccount4 sa0 = new SavingsAccount4(1, 21325302, 0.015);
        SavingsAccount4 sa1 = new SavingsAccount4(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();
    }
};

2.第五章：增添静态属性和方法

class SavingsAccount5 {
    private static double total;
    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;
        total += 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
    public SavingsAccount5(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 int 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(int date, double amount){
        record(date, amount);
    }
    //取出现金
    public 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
    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){
        SavingsAccount4 sa0 = new SavingsAccount4(1, 21325302, 0.015);
        SavingsAccount4 sa1 = new SavingsAccount4(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();
        System.out.println("Total: " + SavingsAccount5.getTotal());
    }
}

3.第六章：增添字符串，对象数组

public class Date {	//日期类
        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 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
        boolean isLeapYear(){	//判断当年是否为闰年
            return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
        }
        public void show(){
            System.out.println(getYear() + "-" + getMonth() + "-" + getDay());
        }	//输出当前日期
        //计算两个日期之间差多少天
        public 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
        SavingsAccount accounts0 = new SavingsAccount(date, "S3755217", 0.015);
        SavingsAccount accounts1 = new SavingsAccount(date, "02342342", 0.015);
        //11月份的几笔账目
        accounts0.deposit(new Date(2008, 11, 5), 5000, "salary");
        accounts1.deposit(new Date(2008, 11, 25), 10000, "sell stock 0323");
        //12月份的几笔账目
        accounts0.deposit(new Date(2008, 12, 5), 5500, "salary");
        accounts1.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();
        accounts0.settle(new Date(2009, 1, 1));
        accounts0.show();
        System.out.println();
        accounts1.settle(new Date(2009, 1, 1));
        accounts1.show();
        System.out.println();
        System.out.println("Total: " + SavingsAccount.getTotal());
    }
}

class SavingsAccount {
    private static double total = 0;
    private String id;                //账号
    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

    //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;
        System.out.println(date + "\t#" + id + "\t" + amount + "\t" + balance+ "\t" + desc);
    }
    private void error(String msg) {
        System.out.println("Error(#" + id + "): " + msg);
    }
    double accumulate( Date date) {
        return accumulation + balance * date.distance(lastDate);
    }
    public String getId() { return id; }
    public double getBalance() { return balance; }
    public double getRate() { return rate; }
    public static double getTotal() { return total; }

    //获得到指定日期为止的存款金额按日累积值
    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("\t#" + id + " created");
    }
    public void deposit( Date date, double amount, String desc) {
        record(date, amount, desc);
    }

    public void withdraw(Date date, double amount, String desc) {
        if (amount > getBalance())
            error("not enough money");
        else
            record(date, -amount, desc);
    }

    public void settle( Date date) {
        double interest = accumulate(date) * rate/ date.distance(new Date(date.getYear() - 1, 1, 1));
        if (interest != 0)
            record(date, interest, "interest");
        accumulation = 0;
    }

    public void show()  {
        System.out.println(id + "\tBalance: " + balance);
    }
}

4.第七章：继承与派生，抽象出父类，增添子类

package SavingsAccount7;

public class Account {
    private String id;    //帐号
    private double balance;    //余额
    private static double total;
    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
    //供派生类调用的构造函数，id为账户
    protected Account( Date date,String id){
        this.id=id;
        this.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( Date date, double amount,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(String msg){
        System.out.println("Error(#" + id + "): " + msg);
    }
    public String getId()  { return id; }
    public double getBalance()  { return balance; }
    public static double getTotal() { return total; }
    //显示账户信息
    void show(){
        System.out.println(id + "\tBalance: " + balance);
    }
}

public class Accumulator {
    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( Date date, double value) {
        this.lastDate=date;
        this.value=value;
        this.sum=0;
    }
    //获得到日期date的累加结果
    public double getSum( Date date)  {
        return sum + value * date.distance(lastDate);
    }

    //在date将数值变更为value
    public void change( 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( Date date, double value) {
        lastDate = date;
        this.value = value;
        sum = 0;
    }
}

public class CreditAccount extends Account{
    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

    final private double getDebt()  {	//获得欠款额
        double balance = getBalance();
        return (balance < 0 ? balance : 0);
    }
    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;
        this.acc=new Accumulator(date, 0);
    }
    //构造函数
    final double getCredit()  { return credit; }
    final double getRate(){ return rate; }
    final double getFee() { return fee; }
    final double getAvailableCredit() {	//获得可用信用
        if (getBalance() < 0)
            return credit + getBalance();
        else
            return credit;
    }

    // 存入现金
    void deposit(final Date date, double amount,final String desc) {
        record(date, amount,desc);
        acc.change(date, getDebt());
    }

    // 取出现金
    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，每年1月1日调用一次该函数
    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());
    }


    final void show(){
        super.show();
        System.out.println("\tAvailable credit:" + getAvailableCredit());
    }
}

class Date {
    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 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
    boolean isLeapYear() {	//判断当年是否为闰年
        return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
    }
    void show() {
        System.out.println(getYear() + "-" + getMonth() + "-" + getDay());
    }		//输出当前日期
    //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
        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);
        //11月份的几笔账目
        sa1.deposit(new Date(2008, 11, 5), 5000, "salary");
        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.settle(new Date(2008, 12, 1));
        //12月份的几笔账目
        ca.deposit(new Date(2008, 12, 1), 2016, "repay the credit");
        sa1.deposit(new Date(2008, 12, 5), 5500, "salary");
        //结算所有账户
        sa1.settle(new Date(2009, 1, 1));
        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();
        sa1.show();System.out.println();
        sa2.show(); System.out.println();
        ca.show(); System.out.println();
        System.out.println("Total: " + Account.getTotal());

    }
}

public class SavingsAccount extends Account{
    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( Date date, String id, double rate){
        super(date, id);
        this.rate=rate;
        this.acc=new Accumulator(date, 0);
    }
    public double getRate()  { return rate; }
    //存入现金
    public void deposit( Date date, double amount, String desc){
            record(date, amount, desc);
            acc.change(date, getBalance());
        }
    //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);
            acc.change(date, getBalance());
        }
    }
    //结算利息，每年1月1日调用一次该函数
    public void settle( Date date){
        double interest = acc.getSum(date) * rate	//计算年息
                / date.distance(new Date(date.getYear() - 1, 1, 1));
        if (interest != 0)
            record(date, interest, "interest");
        acc.reset(date, getBalance());
    }
}

5.第八章：多态特性

public abstract class Account {
    private String id;	//帐号
    private double balance;	//余额
    private static double total=0; //所有账户的总金额
    final String getId() { return id; }
    final double getBalance() {	return balance;}
    static double getTotal() {	return total;}

    protected Account(final Date date, final String id){
        this.id=id;
        this.balance=0;
        date.show();
        System.out.println("\t#" + id + "created");
    }

    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);
    }

    void show() {
        System.out.print(id + "\tBalance: " + balance);
    }
    //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

    protected final void error(final String msg)  {
        System.out.println("Error(#" + id + "): " + msg +"\n");
    }

}

public class Accumulator {
    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

    Accumulator(final Date date, double value) {
        this.lastDate = date;
        this.value = value;
        this.sum = 0;
    }

    // 获得到日期date的累加结果
    final double getSum(final Date date) {
        return sum + value * (date.getTotalDays()-lastDate.getTotalDays());
    }

    // 在date将数值变更为value
    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
    void reset(final Date date, double value) {
        lastDate = date;
        this.value = value;
        sum = 0;
    }
}

public class CreditAccount extends Account {
    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

    final private double getDebt()  {	//获得欠款额
        double balance = getBalance();
        return (balance < 0 ? balance : 0);
    }
    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;
        this.acc=new Accumulator(date, 0);
    }
    //构造函数
    final double getCredit()  { return credit; }
    final double getRate(){ return rate; }
    final double getFee() { return fee; }
    final double getAvailableCredit() {	//获得可用信用
        if (getBalance() < 0)
            return credit + getBalance();
        else
            return credit;
    }

    // 存入现金
    void deposit(final Date date, double amount,final String desc) {
        record(date, amount,desc);
        acc.change(date, getDebt());
    }

    // 取出现金
    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，每年1月1日调用一次该函数
    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());
    }


    final void show(){
        super.show();
        System.out.println("\tAvailable credit:" + getAvailableCredit());
    }

}

public class Date {
    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 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

    final int getYear() {
        return year;
    }
    int getTotalDays() {
        return this.totalDays;
    }

    final int getMonth() {
        return month;
    }

    final int getDay() {
        return day;
    }

    final 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

    final boolean isLeapYear() {	//判断当年是否为闰年
        return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
    }

    final void show() {
        System.out.print( getYear()+ "-" + getMonth()+"-" + getDay());//输出当前日期
    }
    //计算两个日期之间差多少天

}

import java.util.Scanner;
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
        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" );
        Scanner sc = new Scanner(System.in);
        char cmd = '0';
        do {
            //显示日期和总金额
            date.show();
            System.out.println( "\tTotal: " + Account.getTotal() + "\tcommand> ");

            int index, day;
            double amount;
            String desc;

            System.out.println("请输入指令 cmd：");
            cmd= sc.next().charAt(0);
            switch (cmd) {
                case 'd':	//存入现金
                    System.out.println("请输入账户数组下标index：");
                    index=sc.nextInt();
                    System.out.println("请输入存款金额amount：");
                    amount=sc.nextDouble();
                    System.out.println("请输入存款项目名称desc：");
                    desc=sc.nextLine();
                    accounts[index].deposit(date, amount, desc);
                    break;
                case 'w':	//取出现金
                    System.out.println("请输入账户数组下标index：");
                    index=sc.nextInt();
                    System.out.println("请输入取款金额amount：");
                    amount=sc.nextDouble();
                    System.out.println("请输入取款项目名称desc：");
                    desc=sc.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();
                    }
                    break;
                case 'c':	//改变日期
                    System.out.println("请输入日期day：");
                    day=sc.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 < n; i++)
                        accounts[i].settle(date);
                    break;
            }
        } while (cmd != 'e');
        sc.close();
    }
}

public class SavingsAccount extends Account {
    private Accumulator acc;    //辅助计算利息的累加器
    private double rate;        //存款的年利率

    final double getRate() {
        return rate;
    }

    // 构造函数
    SavingsAccount(final Date date, String id, double rate) {
        super(date, id);
        this.rate = rate;
        this.acc = new Accumulator(date, 0);
    }

    // 存入现金
    void deposit(final Date date, double amount, final String desc) {
        record(date, amount, desc);
        acc.change(date, getBalance());
    }

    // 取出现金
    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
    void settle(final Date date) {
        if (date.getMonth() == 1) {    //每年的一月计算一次利息
            double interest = acc.getSum(date) * rate
                    / (date.getTotalDays() - (new Date(date.getYear() - 1, 1, 1)).getTotalDays());
            if (interest != 0)
                record(date, interest, "interest");
            acc.reset(date, getBalance());
        }

    }
}

6.第九章：使用容器代替数组

package SavingsAccount9;

public abstract class Account {
    private String id;	//帐号
    private double balance;	//余额
    private static double total=0; //所有账户的总金额
    final String getId() { return id; }
    final double getBalance() {	return balance;}
    static double getTotal() {	return total;}

    protected Account(final Date date, final String id){
        this.id=id;
        this.balance=0;
        date.show();
        System.out.println("\t#" + id + "created");
    }

    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);
    }

    void show() {
        System.out.print(id + "\tBalance: " + balance);
    }
    //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

    protected final void error(final String msg)  {
        System.out.println("Error(#" + id + "): " + msg +"\n");
    }

}

package SavingsAccount9;

public class Accumulator {
    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

    Accumulator(final Date date, double value) {
        this.lastDate = date;
        this.value = value;
        this.sum = 0;
    }

    // 获得到日期date的累加结果
    final double getSum(final Date date) {
        return sum + value * (date.getTotalDays()-lastDate.getTotalDays());
    }

    // 在date将数值变更为value
    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
    void reset(final Date date, double value) {
        lastDate = date;
        this.value = value;
        sum = 0;
    }
}

public class CreditAccount extends Account{
    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

    final private double getDebt()  {	//获得欠款额
        double balance = getBalance();
        return (balance < 0 ? balance : 0);
    }
    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;
        this.acc=new Accumulator(date, 0);
    }
    //构造函数
    final double getCredit()  { return credit; }
    final double getRate(){ return rate; }
    final double getFee() { return fee; }
    final double getAvailableCredit() {	//获得可用信用
        if (getBalance() < 0)
            return credit + getBalance();
        else
            return credit;
    }

    // 存入现金
    void deposit(final Date date, double amount,final String desc) {
        record(date, amount,desc);
        acc.change(date, getDebt());
    }

    // 取出现金
    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，每年1月1日调用一次该函数
    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());
    }


    final void show(){
        super.show();
        System.out.println("\tAvailable credit:" + getAvailableCredit());
    }
}

public class Date {
    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 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

    final int getYear() {
        return year;
    }
    int getTotalDays() {
        return this.totalDays;
    }

    final int getMonth() {
        return month;
    }

    final int getDay() {
        return day;
    }

    final 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

    final boolean isLeapYear() {	//判断当年是否为闰年
        return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
    }

    final void show() {
        System.out.print( getYear()+ "-" + getMonth()+"-" + getDay());//输出当前日期
    }
    //计算两个日期之间差多少天
}

import java.util.ArrayList;
import java.io.*;
public class Main {
    public static void main(String[] args) {
        Date date=new Date(2008, 11, 1);	//起始日期
        ArrayList<Account> accounts=new ArrayList<Account>();//创建账户数组，元素个数为0
        System.out.println("(a)add account (d)deposit (w)withdraw (s)show (c)change day (n)next month (e)exit");
        char cmd='0';
        Scanner sc = new Scanner(System.in);
        do {
            //显示日期和总金额
            date.show();
            System.out.println("\tTotal: "+Account.getTotal()+"\tcommand> ");

            char type='0';
            int index, day;
            double amount, credit, rate, fee;
            String id, desc;
            System.out.println("请输入指令 cmd：");
            cmd= sc.next().charAt(0);
            switch (cmd) {
                case 'a':	//增加账户
                    try {
                        System.out.println("请输入账户类型（s:SavingAccount 其它:CreditAccount):");
                        type=(char) System.in.read();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    System.out.println("请输入id：");
                    id=sc.next();
                    if (type == 's') {
                        System.out.println("请输入存款的年利率rate：");
                        rate=sc.nextDouble();
                        accounts.add(new SavingsAccount(date, id, rate));
                    } else {
                        System.out.println("请输入信用额度credit：");
                        credit=sc.nextDouble();
                        System.out.println("请输入欠款的日利率rate：");
                        rate=sc.nextDouble();
                        System.out.println("请输入信用卡年费fee：");
                        fee=sc.nextDouble();
                        accounts.add(new CreditAccount(date, id, credit, rate, fee));
                    }
                    break;
                case 'd':	//存入现金
                    System.out.println("请输入账户数组下标index：");
                    index=sc.nextInt();
                    System.out.println("请输入存款金额amount：");
                    amount=sc.nextDouble();
                    System.out.println("请输入存款项目名称desc：");
                    desc=sc.nextLine();
                    accounts.get(index).deposit(date, amount, desc);
                    break;
                case 'w':	//取出现金
                    System.out.println("请输入账户数组下标index：");
                    index=sc.nextInt();
                    System.out.println("请输入取款金额amount：");
                    amount=sc.nextDouble();
                    System.out.println("请输入取款项目名称desc：");
                    desc=sc.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++) {
                        System.out.print("[" + i + "] ");
                        accounts.get(i).show();
                        System.out.println();
                    }
                    break;
                case 'c':	//改变日期
                    System.out.println("请输入日期day：");
                    day=sc.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);
                    break;
            }
        } while (cmd != 'e');
        sc.close();
        accounts.clear();
    }
}

public class SavingsAccount extends Account{
    private Accumulator acc;	//辅助计算利息的累加器
    private double rate;		//存款的年利率
    final double getRate() { return rate; }
    // 构造函数
    SavingsAccount(final Date date, String id, double rate) {
        super(date, id);
        this.rate=rate;
        this.acc=new Accumulator(date, 0);
    }
    // 存入现金
    void deposit(final Date date, double amount,final String desc) {
        record(date, amount, desc);
        acc.change(date, getBalance());
    }

    // 取出现金
    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
    void settle(final Date date) {
        if (date.getMonth() == 1) {	//每年的一月计算一次利息
            double interest = acc.getSum(date) * rate
                    / (date.getTotalDays() - (new Date(date.getYear() - 1, 1, 1)).getTotalDays());
            if (interest != 0)
                record(date, interest, "interest");
            acc.reset(date, getBalance());
        }

    }
}