Exception in thread "main" java.lang.NoSuchMethodError

Hi everybody,

I'm working a program assignment for school. I thought my code was
good but it won't run. It compiles successfully but gives me this
error during runtime:

Exception in thread "main" java.lang.NoSuchMethodError

Do you have any advice? My code is below.

Thanks in advance,

Don

<-------------------------------------------------------------------------------------------------------------------------------------------------------

/*
    Title: Mortgage Payment Calculator
    Programmer: Don
    Date: May 14, 2007
    Filename: MortPayCalc.java
    Purpose: This program calculates mortgage payment amounts.
*/

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

class MortPayCalc2
{

    private boolean end = false;
    private DecimalFormat newFormat = new DecimalFormat ("$#,###.00");
    private double dPrincipal, dAPR, dPayment, dCurrMonthInterest,
dCurrMonthPrincipal, dLoanBalance;
    private double dLoanPrincipal = dPrincipal;
    private int iTerm, iPayments, iOption;
    private String Principal;
    private String Table = "";

    public void GetPrincipal()
    {

      Principal = JOptionPane.showInputDialog(null, "Enter Loan
Principal (ex. 20000): ", "Mortgage Payment
Calculator",JOptionPane.QUESTION_MESSAGE);
      dPrincipal = Double.parseDouble(Principal);

    }

    public void GetLoanTerms()
    {

        Object[] possibilities = {"Loan A", "Loan B", "Loan C"};
      String s = (String)JOptionPane.showInputDialog(null,"Please choose
your loan terms:\n",
        "Mortgage Payment
Calculator",JOptionPane.PLAIN_MESSAGE,null,possibilities,"Loan A");

        int [] Terms = {7, 15, 30};
        double [] Rates = {5.35, 5.5, 5.75};

        if (s == "Loan A")
            {
      iTerm = Terms[0];
      dAPR = Rates[0];
      }
        else if (s == "Loan B")
      {
      iTerm = Terms[1];
      dAPR = Rates[1];
      }
        else
      {
      iTerm = Terms[2];
      dAPR = Rates[2];
      }

    }

    public void CalculatePayment()
    {

        iPayments = iTerm * 12;
        dAPR = dAPR/100/12;
        dPayment = (dPrincipal*Math.pow((1+dAPR),iPayments)*dAPR)/
(Math.pow((1+dAPR),iPayments)-1);

    }

    public void CalculateAmortization()
    {

        for (int i = 0; i < iPayments; i++)
      {
      dCurrMonthInterest = dLoanPrincipal * dAPR;
      dCurrMonthPrincipal = dPayment - dCurrMonthInterest;
      dLoanBalance = dLoanPrincipal - dCurrMonthPrincipal;
      dLoanPrincipal = dLoanBalance;
      String Row = String.format(newFormat.format(dCurrMonthPrincipal) +
" " + newFormat.format(dCurrMonthInterest) + " " +
newFormat.format(dLoanBalance) + "\n");
      Table = Table + Row;
        }
    }

    public void DisplayResults()
    {

        iOption = JOptionPane.showConfirmDialog(null,
        "Loan Principal: " + newFormat.format(dPrincipal) + "\n" +
          "Loan Annual Percentage Rate: " + dAPR + "%" + "\n" +
      "Loan Term In Years: " + iTerm + " years" + "\n" +
      "Monthly Loan Payment Amount: " + newFormat.format(dPayment) +
"\n" +
        Table + "\n\n" +
      "Recalculate?",
         "Mortgage Payment Calculator", JOptionPane.YES_NO_OPTION);

    }

    public void main(String[] args)
    {

        while (end == false)
        {

            GetPrincipal();
            GetLoanTerms();
            CalculatePayment();
            CalculateAmortization();
            DisplayResults();

            if (iOption == JOptionPane.YES_OPTION)
          {
           end = false;
          }
          else
          {
           System.exit(0);
          }

        }

    }

}