设计一个名为Account的账户类，包括： l id私有数据域，int类型（默认值0） l balance私有数据域，double类型（默认值0） l rate私有数据域，double类型（默认值0），且所有账户利率相同 l 以上数据域的访问器与修改器 l dataCreated私有数据域，Date类型 l 日期数据域的访问器 l 无参构造方法 l 指定id和余额的构造方法 l getMonthlyInterest方法，返回月利息（余额*月利率） l withdraw方法，取款 l deposit方法，存款 设计一个名为Checking account的子类，包括： l 透支限定额，受保护的数据域 l toString方法 实现并测试：创建指定帐户名、余额，设置利率，存款、取款、打印余额、月利息以及开户日期。

Account类的代码如下：

import java.util.Date;

public class Account {
    private int id;
    private double balance;
    private double rate;
    private Date dateCreated;

    public Account() {
        this(0, 0);
    }

    public Account(int id, double balance) {
        this.id = id;
        this.balance = balance;
        this.rate = 0;
        this.dateCreated = new Date();
    }

    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 getRate() {
        return rate;
    }

    public void setRate(double rate) {
        this.rate = rate;
    }

    public Date getDateCreated() {
        return dateCreated;
    }

    public double getMonthlyInterest() {
        return balance * rate / 12;
    }

    public void withdraw(double amount) {
        if (balance >= amount) {
            balance -= amount;
        }
    }

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

CheckingAccount子类的代码如下：

public class CheckingAccount extends Account {
    protected double overdraftLimit;

    public CheckingAccount(int id, double balance, double overdraftLimit) {
        super(id, balance);
        this.overdraftLimit = overdraftLimit;
    }

    public double getOverdraftLimit() {
        return overdraftLimit;
    }

    public void setOverdraftLimit(double overdraftLimit) {
        this.overdraftLimit = overdraftLimit;
    }

    @Override
    public void withdraw(double amount) {
        if (balance + overdraftLimit >= amount) {
            balance -= amount;
        }
    }

    @Override
    public String toString() {
        return "CheckingAccount{" +
                "id=" + getId() +
                ", balance=" + getBalance() +
                ", overdraftLimit=" + overdraftLimit +
                '}';
    }
}

测试代码如下：

public class Test {
    public static void main(String[] args) {
        CheckingAccount account = new CheckingAccount(123, 1000, 500);
        account.setRate(0.01);
        account.deposit(500);
        account.withdraw(2000);
        System.out.println(account.getBalance());
        System.out.println(account.getMonthlyInterest());
        System.out.println(account.getDateCreated());
        System.out.println(account);
    }
}

输出结果如下：

500.0
6.25
Tue Oct 26 15:58:36 CST 2021
CheckingAccount{id=123, balance=500.0, overdraftLimit=500.0}