java - Java JOptionPane 输出

Question

谁能告诉我我在这里做错了什么。我需要从用户输入计算一些值到一些 JOptionPane-input-dialog-boxes，然后输出答案。

我将非常感谢我得到的任何帮助。提前致谢！

1. 输入
   • 要比较的贷款数量（可能超过 1 个）
   • 售价
   • 首付
   • 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. 加工
   • 对于给定的利率和年数，您将需要计算 d 部分中列出的每个方案的每月付款。
3. 输出
   • 售价
   • 首付
   • 贷款额度
   • 每个场景的列表
     
     • 兴趣
     • 年
     • 支付

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）强迫使用多个 JOption 窗格进行输入和输出，那么这就是我解决问题的方法。这仅供您参考……如果您将其作为自己的工作提交，您的老师会闻到老鼠的味道，而巨魔也有谷歌。

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”由一组Loan对象表示......即：每个“贷款选项”都由该类的一个实例表示，Loan该类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。这比您用来存储贷款属性的技术（称为“并行数组”）更好的方法......嗯，嗯，它有点过时了，事实上它有一个（油腻的）鲻鱼，它穿着（太紧）橙色狩猎服，头带（深红粉色）……在 80 年代看起来并不好看，而现在，它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！

该类Loan还有几个方便的“计算字段”来为我们进行计算。这意味着，如果将来我们计算还款的方式因某种原因发生变化，我们只有一个地方可以改变它，而使用贷款的一切（可能是读取、写入、置换、总计、收回甚至批发贷款）确实不必改变......他们只是“免费”获得改变。

在这个人为的用例中，我们所有的贷款都将针对相同的金额，只有利率和期限有所不同......所以Loan该类还有一个static名为“原则”的变量，它持有所有实例的“共同”原则贷款班。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，我希望你能从另一种方法中学到一些东西，以解决你在自己做这个练习时可能发现的一些子问题。对未来的一个提示：为这个练习获取你的同学的代码并通读它......你可以从其他人如何处理事情中学到很多东西。

干杯。基思。

Answer 2

for (int i = 0; i < numberOfLoans; i++)
{
    sb.append(/*...snip...*/ Arrays.toString(annualInterestRatesArray), Arrays.toString(numberOfYearsArray), Arrays.toString(monthlyPaymentArray));
}

你还没有告诉我们问题是什么，但我认为这不是你想要的。每次循环进行时，您都要求程序打印出整个三个数组。相反，您可能想要访问每笔贷款的特定数组元素，对吧？就像是...

for (int i = 0; i < numberOfLoans; i++)
{
    sb.append(/*...snip...*/ annualInterestRatesArray[i], numberOfYearsArray[i], monthlyPaymentArray[i]);
}

Answer 3

String.format("\t \t \t \t \t \n", sellingPrice, ...

那只会输出5个标签。你要

String.format("%s %s %s %s %s %n", sellingPrice, ...

Answer 4

现在您需要检查result返回的 by showMessageDialog()，如下所示。

Answer 5

你JOptionPane.showMessageDialog(null...在一个 for 循环中。所以它将显示它的次数与 numberOfLoans2 的值一样多。如果你不想要那个，移动你的

 String toDisplay = sb.toString();

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

在for循环之外。

Answer 6

在您的答案打印方法中，该numberOfLoans2变量用于两个地方：在 for 循环中进行多次打印（外循环）和在 for 循环中进行数学计算（内循环）。可能外面的那个没用了，所以去掉它，结果可能会显示一次。请记住删除}循环元素末尾的结尾以保持结构正常:)