Java黑皮书课后题第11章：11.3（Account类的子类）在编程练习题9.7中定义了一个Account类来对一个银行账户建模。一个账户有账号、余额、年利率、开户日期等属性，以及存款和取款等方法

• 题目（续）
• 题目中提到的编程练习题9.7：以下代码直接利用即可
• Test03_checking_account：支票账户
• Test03_saving_account
• Test03：测试程序（创建三个对象并调用toString方法）
• 总UML图

画出这些类的UML图并实现这些类。编写一个测试程序，创建Account、SavingsAccount和CheckingAccount的对象，然后调用它们的toString()方法

省流助手：四个私有数据域 + 无参有参构造方法 + id balance annualInterestRate三个数据域的setter和getter方法 + dateCreated的访问器方法 + getMonthlyInterestRate方法 + getMonthlyInterest方法 + withDraw方法 + deposit方法

import java.util.Date;

public class Test2_Account {
    // 四个私有数据域
    private int id = 0;
    private double balance = 0.0;
    private double annualInterestRate = 0.0;
    private Date dateCreated;

    // 无参构造方法
    public Test2_Account(){
    }
    // 有参构造方法
    public Test2_Account(int id, double balance){
        this.id = id;
        this.balance = balance;
    }
    // id balance annualInterestRate的setter和getter
    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;
    }
    // dateCreated的访问器方法
    public Date getDateCreated(){
        return dateCreated;
    }

    // getMonthlyInterestRate方法
    public double getMonthlyInterestRate(){
        return annualInterestRate / 1200;
    }

    // getMonthlyInterest方法
    public double getMonthlyInterest(){
        return annualInterestRate * balance / 1200;
    }

    // withDraw方法
    public void withDraw(double num){
         if (num <= balance) balance -= num;
    }

    // deposit方法
    public void deposit(double num){
        balance += num;
    }
	@Override
    public String toString() {
        return "Test03_Account{" +
                "id=" + id +
                ", balance=" + balance +
                ", annualInterestRate=" + annualInterestRate +
                ", dateCreated=" + dateCreated +
                '}';
    }
}

本类UML图：

public class Test03_checking_account extends Test03_Account{
    public double overDraftLimit = 0;

    public Test03_checking_account(){
    }
    public Test03_checking_account(double overDraftLimit){
        this.overDraftLimit = overDraftLimit;
    }

    @Override
    public String toString() {
        return "Test03_checking_account{" +
                "overDraftLimit=" + overDraftLimit +
                "} " + super.toString();
    }
}

public class Test03_saving_account extends Test03_Account{
    private double minBalance = 0.0;
}

public class Test03 {
    public static void main(String[] args) {
        // 创建Account
        Test03_Account ta = new Test03_Account();
        ta.toString();
        // 创建Savings-Account
        Test03_saving_account sa = new Test03_saving_account();
        sa.toString();
        // 创建CheckingAccount
        Test03_checking_account ca = new Test03_checking_account();
        ca.toString();
    }
}