程序中存款和取款方式的问题

Question

在我运行SpecialSavingsDriver时，我需要帮助找出为什么输出中没有我的利息和存款数字：

Saver 1
New Monthly Savings Balance After Interest: 27958.33
Saver 2
New Monthly Savings Balance After Interest: 4933.33
Saver 1
New Monthly Savings Balance After Interest: 49240.28
Saver 2
New Monthly Savings Balance After Interest: 6431.11

我确实让它在我的SavingsAccountClass中正确地添加了兴趣。我在SpecialSavings类中的退出方法似乎也不起作用。任何援助都将得到极大的支持。以下是我正在努力完成的任务的概要：

第1部分

创建一个类SavingsAccount。使用静态类变量来存储每个保护程序的annualInterestRate。该类的每个对象都包含一个私有实例变量savingsBalance，指示保存程序当前存款的数量。提供方法calculateMonthlyInterest，通过将余额乘以annualInterestRate除以12计算月利息；此利息应添加到savingsBalance中。提供一个静态方法modifyInterestRate，将annualInterestRate设置为新值。编写一个驱动程序来测试类SavingsAccount。实例化两个不同的savingsAccount对象，saver1和saver2，余额分别为2000.00美元和3000.00美元。将annualInterestRate设置为4%，然后计算每月利息，并为每个储户打印新的余额。然后将annualInterestRate设置为5%，计算下一个月的利息，并为每个储户打印新的余额。

第2部分

编写另一个类SpecialSavings，将SavingsAccount扩展到对余额超过10K的账户支付10%的利息。还提供了存取款的方法。编写一个驱动程序来测试类SpecialSavings。实例化两个不同的savingsAccount对象，saver1和saver2，余额分别为2000.00美元和3000.00美元。进行一些存款和取款，并显示每个帐户的余额和利息。

再次感谢你！

public class SavingsAccountDriver {

    public static void main(String[] args) {
        SavingsAccount saver1 = new SavingsAccount();
        SavingsAccount saver2 = new SavingsAccount();
        
        saver1.setsavingsBalance(2000);
        saver2.setsavingsBalance(3000);
        
        SavingsAccount.modifyInterestRate(0.04);
        
        saver1.calculateMonthlyInterest();
        saver2.calculateMonthlyInterest();
        
        System.out.printf("\nSaver 1\nNew Monthly Savings Balance After Interest: %.2f",saver1.getsavingsBalance());
        System.out.printf("\nSaver 2\nNew Monthly Savings Balance After Interest: %.2f",saver2.getsavingsBalance());
        
        SavingsAccount.modifyInterestRate(0.05);
        
        saver1.calculateMonthlyInterest();
        saver2.calculateMonthlyInterest();

        System.out.printf("\nSaver 1\nNew Monthly Savings Balance After Interest: %.2f",saver1.getsavingsBalance());
        System.out.printf("\nSaver 2\nNew Monthly Savings Balance After Interest: %.2f",saver2.getsavingsBalance());
    }

public class SavingsAccount {
    
    public static double annualInterestRate;
    public double savingsBalance;
    
    /*
     * Constructor
     * */
    public SavingsAccount() {
        annualInterestRate = 0;
        savingsBalance = 0;
    }
    /*
     * Overloaded
     * */
    public SavingsAccount(double savingsBalance) {
        this.savingsBalance = savingsBalance;
    }
    /*
     * Calculates Monthly Interest from savings balance and interest rate
     * */
    public void calculateMonthlyInterest() {
        savingsBalance += savingsBalance*annualInterestRate/12;
    }
    /*
     * Interest Rate modifier
     * */
    public static void modifyInterestRate(double newInterestRate) {
        annualInterestRate = newInterestRate;
    }
    /*
     * Returns new Savings Balance
     * */
    public double getsavingsBalance() {
        return savingsBalance;
    }   
    /*
     * Sets new savings balance after interest
     * */
    public void setsavingsBalance(double savingsBalance) {
        this.savingsBalance = savingsBalance;
    }

    /*
     * Returns Interest Rate
     * */
    public double getannualInterestRate() {
        return annualInterestRate;
    }
}

public class SpecialSavings extends SavingsAccount {
    
    public SpecialSavings() {
        annualInterestRate = 0;
        savingsBalance = 0;
    }   
    
    public SpecialSavings(double savingsBalance) {
        super(savingsBalance);
    }
    
    public void calculateMonthlyInterest() {
        if(getsavingsBalance()>10000) {
            modifyInterestRate(10);
        }else {
            modifyInterestRate(4);
        }
        super.calculateMonthlyInterest();
    }
    
    public void deposit(double amount) {
        savingsBalance+=amount;
    }
    
    public void withdraw(double amount) {
        savingsBalance-=amount;
    }
    
}

public class SpecialSavingsDriver {

    public static void main(String[] args) {
        SpecialSavings saver1 = new SpecialSavings();
        SpecialSavings saver2 = new SpecialSavings();
        
        saver1.setsavingsBalance(2000);
        saver2.setsavingsBalance(3000);
        
        SavingsAccount.modifyInterestRate(0.04);
        
        saver1.deposit(13000);
        saver1.deposit(250);
        saver2.deposit(350);
        saver2.deposit(350);
        
        saver1.calculateMonthlyInterest();
        saver2.calculateMonthlyInterest();
        
        System.out.printf("\nSaver 1\nNew Monthly Savings Balance After Interest: %.2f",saver1.getsavingsBalance());
        System.out.printf("\nSaver 2\nNew Monthly Savings Balance After Interest: %.2f",saver2.getsavingsBalance());
        
        saver1.withdraw(1000);
        saver1.withdraw(100);
        saver2.withdraw(100);
        saver2.withdraw(10);
        
        saver1.calculateMonthlyInterest();
        saver2.calculateMonthlyInterest();
        
        System.out.printf("\nSaver 1\nNew Monthly Savings Balance After Interest: %.2f",saver1.getsavingsBalance());
        System.out.printf("\nSaver 2\nNew Monthly Savings Balance After Interest: %.2f",saver2.getsavingsBalance());

    }

}

Answer 1

我觉得这句话有问题。

savingsBalance*annualInterestRate/12;

它会这样执行：-

(savingsBalance*annualInterestRate)/12;
= (multipliedValue)/12;
= result

我希望你不要这样，为了解决这个问题，你应该用括号

savingsBalance*(annualInterestRate/12);