Java贷款计算器

Question

我正在尝试编写一个贷款计算器。我好像遇到问题了我正在尝试从用户那里获取输入并验证输入。我知道我做错了，问题是我挠头不知道如何做正确。我在 d = getDouble(sc, Prompt); 上看到一条红线和 i = getInt(sc, 提示);据我所知，我的编码不正确。我只是不确定如何修复它。

我还必须验证 continue 语句，但我不确定最好的方法，最后讲师期望代码为 80 行或更少，我对 80 行的看法是正确的。我想我正在寻找一种更好的方法来做到这一点，但作为新手，我正在摸不着头脑，我希望有人能伸出援手。

一如既往，我非常感谢您的帮助。

   import java.util.Scanner;
   import java.text.NumberFormat;

    public class LoanCalculator
    {   
        public static double getDoubleWithinRange(Scanner sc, String prompt, double min, double max)
        {
          double d = 0.0;
          boolean isValid = false;
          while(isValid == false);
           {
                d = getDouble(sc, prompt);
                if (d <= min)
                   {
                   System.out.println("Error! Number must be greater tha 0.0");
                   }
                   else if (d >= max)
                  {
                     System.out.println("Error number must be less than 1000000.0");
                }
                else 
                    isValid = true;
            }
            return d;       
        }
            public static int getIntWithinRange(Scanner sc, String prompt, int min, int max)
        {
            int i = 0;
            boolean isvalid = false;
            while(isvalid == false)
             {
                i = getInt(sc, prompt);
                if (i <= min)
                       System.out.println("Error! Number must be more than 0");
                else if (i >= max)
                    System.out.println("Error! Number must be less than 100");
                else 
                    isvalid = true;
            }   
        }
          public static void main(String[] args)
         {
            System.out.println("Welcome to the loan calculator");
            Scanner sc = new Scanner(System.in);
            String choice = "y";
            while (choice.equalsIgnoreCase("y"))
            {
                System.out.println("DATA ENTRY");
                double loanAmount = getDoubleWithinRange(sc, "Enter loan amount: ", 0.0, 1000000.0);
                double interestRate = getDoubleWithinRange(sc, "Enter yearly interest rate: ", 0, 20);
                int years = getIntWithinRange(sc, "Enter number of years: ", 0, 100);
                int months = years * 12;

                double monthlyPayment = loanAmount * interestRate/
                        (1 - 1/Math.pow(1 + interestRate, months));

                NumberFormat currency = NumberFormat.getCurrencyInstance();
                NumberFormat percent = NumberFormat.getPercentInstance();
                percent.setMaximumFractionDigits(3);
                System.out.println("RESULST");
                System.out.println("Loan Amount" + currency.format(loanAmount));
                System.out.println("Yearly interest rate: " + percent.format(interestRate));
                System.out.println("Number of years: " + years);
                System.out.println("Monthly payment: " + currency.format(monthlyPayment));

                System.out.println();
                System.out.println("Continue? (y/n): ");
                choice =sc.next();
                System.out.println();

            }           
        }
    }

Answer 1

您尚未实现 getDouble(Scanner,String) 和 getInt(Scanner,String)，这就是您看到红线的原因。

因为你已经有一个扫描仪，并且提示字符串将其更改为这个

System.out.print(prompt);
d = sc.nextDouble();

对于整数

System.out.print(prompt);
i = sc.nextInt();