Formula in gui

Question

This program runs except for the "for"loop. Program is supposed to compound quarterly interest and output yearnumber(incrementing up to 20), amount of principal at beginning of year, interest earned, and principal at end of year. I have worked hard on this and it is due today, and so far the professor is awarding me a 20 for my effort. Can anyone please help?
//PROGRAM NAME:  mutualfund
//PROGRAMMER'S NAME:  Rebecca Thompson
//DATE:  February 21, 2005
//PURPOSE:  Calculate compound interest
import javax.swing.*;
import BreezySwing.*;
public class mutualfund extends GBFrame {
   // Declare variables for the window objects
   private JLabel       interestLabel;
   private JLabel         yearsLabel;
   private JLabel       principalLabel;
   private DoubleField interestField;
   private DoubleField principalField;
   private DoubleField yearsField;
   private JButton      calcButton;
   private JTextArea    output;
   // Define the other instance variables
   private double  totalYearsIn;        //The years in fund
   private double  totalBegPrincipal;  //The principal at beginning of each quarter
   private double totalInterestEarn;
   private double totalEndPrincipal;
   // Constructor
   public mutualfund(){
      // Define table heading line
      String header = Format.justify('l', "Years In", 15) +
                      Format.justify('r', "Interest Earned", 15) +
                      Format.justify('r', "Beg. Principal", 20) +
                      Format.justify('r', "End Principal", 20) + "\n";
      // Instantiate the window objects
       interestLabel= addLabel       ("Interest Rate"   ,1,1,1,1);
      principalLabel   = addLabel("Principal Amount $" ,1,2,1,1);
      yearsLabel   = addLabel       ("Years In"        ,1,3,3,1);
       interestField=addDoubleField(0                   ,2,1,1,1);
      principalField = addDoubleField (0               ,2,2,1,1);
      yearsField=   addDoubleField  (0                 ,2,3,1,1);
      calcButton  = addButton      ("Calculate "        ,3,1,1,1);
      output       = addTextArea    (header            ,4,1,3,4);
      // Disable the text area
      // Set the focus to principal field.
      output.setEditable(false);
      principalField.requestFocus();
      // Initialize the totals to 0.
      totalYearsIn = 0;
      totalBegPrincipal = 0;
      totalInterestEarn=0;
      totalEndPrincipal=0;
   // Respond to the command buttons
   public void buttonClicked (JButton buttonObj){
      if (buttonObj == calcButton){
         processInputs();
         displayNumbers (totalYearsIn, totalBegPrincipal, totalInterestEarn, totalEndPrincipal);
      }else{
         calcButton.setEnabled(true);      //
   // Read the  user inputs, compute the formula, format and display the
   // totals.
   private void processInputs(){
      // Declare the local variables
      double years=0;
      double begPrin=0;
      double iRate=0;
      double yrlyPrincipal=0;
      double currentBalance = 0;
       begPrin = principalField.getNumber();
       System.out.println(begPrin);
       years = yearsField.getNumber();
       System.out.println(years);
       iRate = interestField.getNumber();
totalBegPrincipal = begPrin+begPrin;
System.out.println(totalBegPrincipal);
/* This section is commented out because it causes the program not to compile.
Without it the program compiles.  I need help fitting it all together!
      // Calculate the formula.
      for (years = 1; years <=yearsField; ++years){
           totalYearsIn = years;
           totalInterestEarn = begPrin(1+iRate/4);
           totalBegPrincipal = totalBegPrin + totalInterestEarned;
           totalEndPrincipal = totalBegPrincipal * years;
            years = years++;
   // Format for text area.
   private void displayNumbers ( double num1, double num2, double num3, double num4){
      String numberLine = Format.justify ('r', num1, 15, 2) +
                          Format.justify ('r', num2, 15, 2) +
                          Format.justify ('r', num3, 15, 2) +
                          Format.justify ('r', num4,  15,2);
                                    output.append (numberLine + "\n");
   // Display dashes just in case
   private void displayDashes(){
     String dashLine =
                        Format.justify ('r', "----------", 15) +
                        Format.justify ('r', "----------", 15);
      output.append (dashLine + "\n");
//main
   public static void main (String[] args){
      mutualfund theGUI = new mutualfund();
      theGUI.setSize (550, 425);
      theGUI.setVisible (true);
}

Answer 1

What I was trying to do was read the value from the gui field, and then assign that value to a local variable, and then use the local variable within the loop. ie
   double begPrin=0;   this is a local variable
      double iRate=0;
      double yrlyPrincipal=0;
      double currentBalance = 0;
       begPrin = principalField.getNumber();   here is where I read the value from the field    [    /code]
then below here I used the local variable in the formula.  What is the right way?