9.7(Account类)设计一个名为Account的类，包含：

 下面是Java的源代码：

import java.util.Date;

class Account{

    private int id;
    private double balance;
    private double annualInterestRate;
    private Date dataCreated;

    Account(){
        id =1000;
        balance = 2000;
    }
    public Date getDataCreated(){
        Date date = new Date();
        return date;
    }

    public double getMonthlyInterstRate(){
        return annualInterestRate/12;
    }

    public void withDraw(double num){
        balance=balance-num;
    }

    public void deposit(double num){
        balance=balance+num;
    }

    public double getMonthlyInterest(){
        return balance*getAnnualInterestRate();
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public double getBalance() {
        return balance;
    }

    public void setBalance(double balance) {
        this.balance = balance;
    }

    public double getAnnualInterestRate() {
        return annualInterestRate;
    }

    public void setAnnualInterestRate(double annualInterestRate) {
        this.annualInterestRate = annualInterestRate;
    }
}
public class Acount类 {
    public static void main(String[] args) {

        Account a = new Account();
        System.out.println(a.getId());
        System.out.println(a.getBalance());
        a.setId(1122);a.setBalance(20000);a.setAnnualInterestRate(0.045);
        System.out.println(a.getId()+" "+a.getAnnualInterestRate()+" "+a.getBalance());
        a.withDraw(2500);
        System.out.println(a.getBalance());
        a.deposit(3000);
        System.out.println(a.getBalance());

        System.out.println(   a.getMonthlyInterest()
);
        System.out.println(a.getDataCreated().getTime());

    }

}

写类的时候，一开始的时候看起来觉得很多，感觉很难，不想看。后来逐渐的发现，题目非常重要，完全就是翻译题目。