Java JOptionPane 输出

Question

谁能告诉我我做错了什么。我需要从用户输入到一些 JOptionPane 输入对话框中计算一些值，然后输出答案。

如果我得到任何帮助，我将不胜感激。提前致谢!

1. 输入
   • 要比较的贷款数量(可以超过 1)
   • 售价
   • 预付款
   • 对于他们想要比较的每笔贷款，您将询问以下内容
     
     • 利率
     • 年数
2. 处理中
   • 您需要针对给定的利率和年数计算 d 部分中列出的每种情况的每月还款额。
3. 输出
   • 售价
   • 预付款
   • 贷款金额
   • 每个场景的列表
     
     • 兴趣
     • 年
     • 付款

到目前为止，这是我的代码:

    package javamortgagecalculator;
    import javax.swing.JOptionPane;
    import java.util.*;       
    public class JavaMortgageCalculator {
         public static void main(String[] args) {       
              //A. Enter the Number Of Loans to compare
              String numberOfLoansString = JOptionPane.showInputDialog("Enter the Number Of Loans to Compare"); 
              //Convert numberOfLoansString to int
              int numberOfLoans = Integer.parseInt(numberOfLoansString);

              //B. Enter the Selling Price of Home
              String sellingPriceString = JOptionPane.showInputDialog("Enter the Loan Amount");
              //Convert homeCostString to double
              double sellingPrice = Double.parseDouble(sellingPriceString);

              //C. Enter the Down Payment on the Home
              String downPaymentString = JOptionPane.showInputDialog("Enter the down payment on the Home");
              double downPayment = Double.parseDouble(downPaymentString);

              //Get the loanAmount by Subtracting the Down Payment from homeCost
              double loanAmount = sellingPrice - downPayment;

              //D. Ask the following for as many number of loans they wish to compare
              //D1 Get the interest rate
              double[] annualInterestRatesArray = new double[numberOfLoans];
              double[] monthlyInterestRateArray = new double[numberOfLoans];
              int[] numberOfYearsArray = new int[numberOfLoans];
              double[] monthlyPaymentArray = new double[numberOfLoans];
              double[] totalPaymentArray = new double[numberOfLoans];
              int counter = 1;

              for (int i=0; i < numberOfLoans; i++)
              {
                  String annualInterestRateString = JOptionPane.showInputDialog("Enter           the interest rate for Scenario " + counter);
                  double annualInterestRate = Double.parseDouble(annualInterestRateString);
                  annualInterestRatesArray[i] = (annualInterestRate);

                  //Obtain monthly interest rate
                  double monthlyInterestRate = annualInterestRate / 1200;
                  monthlyInterestRateArray[i] = (monthlyInterestRate);

                  //D2 Get the number of years
                  String numberOfYearsString = JOptionPane.showInputDialog("Enter the      number of years for Scenario " + counter);
                  int numberOfYears = Integer.parseInt(numberOfYearsString);
                  numberOfYearsArray[i] = (numberOfYears);

                  //Calculate monthly payment
                  double monthlyPayment = loanAmount * monthlyInterestRate / (1 - 1 / Math.pow(1 + monthlyInterestRate, numberOfYears * 12));
                  //Format to keep monthlyPayment two digits after the decimal point
                  monthlyPayment = (int)(monthlyPayment * 100) / 100.0;
                  //Store monthlyPayment values in an array
                  monthlyPaymentArray[i] = (monthlyPayment);

                  //Calculate total Payment
                  double totalPayment = monthlyPaymentArray[i] * numberOfYears * 12;
                  //Format to keep totalPayment two digits after the decimal point
                  totalPayment = (int)(totalPayment * 100) / 100.0;
                  totalPaymentArray[i] = (totalPayment);

                  counter++;
              }

              StringBuilder sb = new StringBuilder();
              for (int i = 0; i < numberOfLoans; i++) {
                     sb.append(String.format("\t \t \t \t \t \n", sellingPrice, downPayment, loanAmount, Arrays.toString(annualInterestRatesArray),           Arrays.toString(numberOfYearsArray), Arrays.toString(monthlyPaymentArray)));
              }
              String toDisplay=sb.toString();

              JOptionPane.showMessageDialog(null, sb.toString(), toDisplay, JOptionPane.INFORMATION_MESSAGE);             
          }
     }

Answer 1

如果我被迫(大概是被一个伪装成编程老师的大绿色、特别丑陋的巨魔)使用多个 JOption Pane 进行输入和输出，那么我将如何解决这个问题。这仅供您引用...如果您将其作为自己的作业上交，您的老师会闻到老鼠的味道，巨魔也有谷歌。

package forums;
import javax.swing.JOptionPane;
import java.text.DecimalFormat;

/**
 * Compares total cost of mortgages (aka ordinary annuity certains)
 */
public class MortgageCalculator
{
  public static void main(String[] args)
  {
    // 1. input
    final double price = Enter.aDouble("the purchase of the property");
    final double deposit = Enter.aDouble("down payment");
    Loan.setPrinciple(price - deposit);

    int numLoans = Enter.anInteger("number of loans to compare");
    Loan[] loans = new Loan[numLoans];
    for ( int i=0; i<numLoans; ++i ) {
      loans[i] = new Loan(
          Enter.aDouble("Annual interest rate for Loan " + (i+1) + "  (eg: 6.75)") / 100.0 / 12.0
        , Enter.anInteger("number of years for Loan " + (i+1) + "  (eg 20)") * 12
      );
    }

    // 3. Output
    final String caption = 
        "Principle " + Format.money(Loan.getPrinciple())
      + " = Price " + Format.money(price) 
      + " - Deposit " + Format.money(deposit);

    StringBuilder results = new StringBuilder(64 + numLoans * 64);
    results.append("Monthly Rate, Months, Monthly Repayment, Total Repayments\n");
    for ( Loan l : loans ) {
      results.append(String.format("%5s, %d, %13s, %13s\n"
        , Format.percent(l.rate)
        , l.periods
        , Format.money(l.payment())
        , Format.money(l.totalPayment())
      ));
    }
    JOptionPane.showMessageDialog(null, results.toString(), caption, JOptionPane.INFORMATION_MESSAGE);
  }

  static class Format
  {
    static java.text.Format MONEY = new DecimalFormat("$#,###.##");
    static String money(double amount) {
      return MONEY.format(amount);
    }

    static java.text.Format PERCENT = new DecimalFormat("0.###%");
    static String percent(double amount) {
      return PERCENT.format(amount);
    }

    static StringBuilder join(String between, Object... values) {
      StringBuilder result = new StringBuilder(values.length * 16);
      if ( values.length > 0 ) {
        result.append(values[0].toString());
        for ( int i=1; i<values.length; ++i ) {
          result.append(between)
            .append(values[i].toString());
        }
      }
      return result;
    }

  } // end class Format

  static class Enter
  {
    public static int anInteger(String fieldDesc) {
      return Integer.parseInt(JOptionPane.showInputDialog("Enter the "+ fieldDesc));
    }

    public static double aDouble(String fieldDesc) {
      return Double.parseDouble(JOptionPane.showInputDialog("Enter the "+ fieldDesc));
    }
  } // end class Enter

} // end class MortgageCalculator

class Loan
{
  private static double principle = 34324.121221312432;
  final double rate;
  final int periods;

  static void setPrinciple(double principle) {
    if (Loan.principle != 34324.121221312432)
      throw new ReadOnlyException("The Principle can't be changed once set.");
    Loan.principle = principle;
  }

  static double getPrinciple() {
    return Loan.principle;
  }

  /**
   * Initialises a new loan objects
   * @param double rate The interest rate per period, as a percentage.
   *  eg: 0.00625 is 7.5% per annum.
   * @param int periods The number of periods of the loan, typically months.
   */
  Loan(double rate, int periods) {
    this.rate = rate;
    this.periods = periods;
  }

  // 2. processing
  double payment() {
    return principle * rate / (1 - 1/Math.pow(1+rate,periods) );
  }

  double totalPayment() {
    return periods * payment();
  }

}

class ReadOnlyException extends RuntimeException 
{
  private static final long serialVersionUID = 0L;
  public ReadOnlyException(String message) {
    super(message);
  }
}

“要比较的贷款列表”由 Loan 对象数组表示...即:每个“贷款选项”由 Loan 的实例表示> 类，它将特定贷款的所有属性分组为一个整洁的“事物”，然后我们可以将其作为一个整体进行操作。这比你用来存储贷款属性的技术更好，它被称为“平行数组”......好吧，嗯，它有点过时了，事实上它有一条(油腻的)鲻鱼，它穿着(太紧)带有(藏红花粉红色)头带的橙色狩猎服……在八十年代看起来并不好看，现在，很可能会让你被殴打，被捕，或两者兼而有之；取决于您的语言环境...基本上:我们现在有更好的方法!

Loan 类还有一些方便的“计算字段”来为我们进行计算。这意味着如果我们计算还款的方式在未来由于某种原因发生变化，我们只有一个地方可以改变它，而所有使用贷款的东西(可以是读、写、排列、总计、收回，甚至是批发贷款)都可以不必找零……他们只是“免费”找零。

在这个人为设计的用例中，我们所有的贷款金额都相同，只是利率和期限不同...所以 Loan 类也有一个 static 称为“原则”的变量，它包含贷款类的所有实例的“通用”原则。该原则只能设置一次。任何后续设置原则的尝试都将导致抛出 ReadOnlyException。

无论如何，我希望您能从另一种方法中学到一些东西，以解决您在自己进行此练习时可能发现的一些子问题。对 future 的一个提示:捕获你的同学的代码进行这个练习并通读它......你可以从其他人如何处理事情中学到很多东西。

干杯。基思。