储蓄账户计划

Question

我在使用这个程序时遇到了一点问题，即使它已编译。它说我必须添加一个主要方法，但是，我这样做了，我最终得到了 21 个错误。有人请帮助我..

创建一个类 SavingsAccount。使用静态类变量来存储每个储蓄者的年利率。该类的每个对象都包含一个私有实例变量 SavingBalance，指示储蓄者当前的存款金额。提供方法calculateMonthlyInterest，通过将余额乘以annualInterestRate除以12来计算每月利息；这个利息应该加到储蓄余额中。提供一个静态方法 modifyInterestRate 将年利率设置为新值。编写一个驱动程序来测试类 SavingsAccount。实例化两个不同的 SavingAccount 对象 saver1 和 saver2，余额分别为 $2000.00 和 $4000.00。将年利率设置为 3%，然后计算每月利息并打印每个储蓄者的新余额。然后将年利率设置为 5% 并计算下个月的利息并打印每个储蓄者的新余额。

import java.util.Scanner;
public class SavingsAccount{

    private static double annualInterestRate;
    private double savingsBalance;

    public SavingsAccount()
    {
        savingsBalance = 0;
        annualInterestRate = 0;
    }

    public SavingsAccount(double balance)
    {
        savingsBalance = balance;
        annualInterestRate = 0;
    }

    public void calculateMonthlyInterest()
    {
        System.out.println("Current savings balance: " + savingsBalance);
        double monthlyInterest;
        monthlyInterest = (savingsBalance * annualInterestRate)/12;
        savingsBalance = monthlyInterest;
        System.out.println("New savings balance: " + savingsBalance);
    }

    public double getBalance()
    {
        return savingsBalance;
    }
    public static void modifyInterestRate(double newInterestRate)
    {
        annualInterestRate = newInterestRate;
    }
}
class Driver
{
    public static void main(String[] args)
    {
        SavingsAccount saver1 = new SavingsAccount(2000);
        SavingsAccount saver2 = new SavingsAccount(4000);
        saver1.modifyInterestRate(.03);
        saver1.calculateMonthlyInterest();
        saver2.modifyInterestRate(.03);
        saver2.calculateMonthlyInterest();
        saver1.modifyInterestRate(.05);
        saver1.calculateMonthlyInterest();
        saver2.modifyInterestRate(.05);
        saver2.calculateMonthlyInterest();
    }
}

Answer 1

您的代码运行良好。请使用javac SavingsAccount.java 和run 使用java Driver 保存为SavingsAccount.java 和compile。

我compile 和run 你的代码和output 是这个

Answer 2

你可以试试下面的代码。

package savingsaccount;


public class SavingsAccount{

    private static double annualInterestRate;
    private double savingsBalance;

    public SavingsAccount()
    {
        savingsBalance = 0;
        annualInterestRate = 0;
    }

    public SavingsAccount(double balance)
    {
        savingsBalance = balance;
        annualInterestRate = 0;
    }

    public void calculateMonthlyInterest()
    {
        System.out.println("Current savings balance: " + savingsBalance);
        double monthlyInterest;
        monthlyInterest = (savingsBalance * annualInterestRate)/12;
        savingsBalance = monthlyInterest;
        System.out.println("New savings balance: " + savingsBalance);
    }

    public double getBalance()
    {
        return savingsBalance;
    }
    public static void modifyInterestRate(double newInterestRate)
    {
        annualInterestRate = newInterestRate;
    }


    public static void main(String[] args)
    {
        SavingsAccount saver1 = new SavingsAccount(2000);
        SavingsAccount saver2 = new SavingsAccount(4000);
        SavingsAccount.modifyInterestRate(.03);
        saver1.calculateMonthlyInterest();
        SavingsAccount.modifyInterestRate(.03);
        saver2.calculateMonthlyInterest();
        SavingsAccount.modifyInterestRate(.05);
        saver1.calculateMonthlyInterest();
        SavingsAccount.modifyInterestRate(.05);
        saver2.calculateMonthlyInterest();
    }
}

Answer 3

在calculateMonthlyInterest() 中，您需要将每月利息添加到储蓄余额中，而不是重置余额。即

    savingsBalance = monthlyInterest;

应该是：

    savingsBalance += monthlyInterest;

这个更正后的SavingsAccount 类应该是：

public class SavingsAccount{

    private static double annualInterestRate;
    private double savingsBalance;

    public SavingsAccount()
    {
        savingsBalance = 0;
        annualInterestRate = 0;
    }

    public SavingsAccount(double balance)
    {
        savingsBalance = balance;
        annualInterestRate = 0;
    }

    public void calculateMonthlyInterest()
    {
        System.out.println("Current savings balance: " + savingsBalance);
        double monthlyInterest;
        monthlyInterest = (savingsBalance * annualInterestRate)/12;
        savingsBalance += monthlyInterest;
        System.out.println("New savings balance: " + savingsBalance);
    }

    public double getBalance()
    {
        return savingsBalance;
    }
    public static void modifyInterestRate(double newInterestRate)
    {
        annualInterestRate = newInterestRate;
    }
}

Answer 4

将 main 方法放在 SavingsAccount 类中。

这样，

public class SavingsAccount{

   private static double annualInterestRate;
    private double savingsBalance;

    public SavingsAccount()
    {
        savingsBalance = 0;
        annualInterestRate = 0;
    }

    public SavingsAccount(double balance)
    {
        savingsBalance = balance;
        annualInterestRate = 0;
    }

    public void calculateMonthlyInterest()
    {
        System.out.println("Current savings balance: " + savingsBalance);
        double monthlyInterest;
        monthlyInterest = (savingsBalance * annualInterestRate)/12;
        savingsBalance = monthlyInterest;
        System.out.println("New savings balance: " + savingsBalance);
    }

    public double getBalance()
    {
        return savingsBalance;
    }
    public static void modifyInterestRate(double newInterestRate)
    {
        annualInterestRate = newInterestRate;
    }

    public static void main(String[] args)
    {
        SavingsAccount saver1 = new SavingsAccount(2000);
        SavingsAccount saver2 = new SavingsAccount(4000);
        saver1.modifyInterestRate(.03);
        saver1.calculateMonthlyInterest();
        saver2.modifyInterestRate(.03);
        saver2.calculateMonthlyInterest();
        saver1.modifyInterestRate(.05);
        saver1.calculateMonthlyInterest();
        saver2.modifyInterestRate(.05);
        saver2.calculateMonthlyInterest();
    }
}