Morgage Calculator SR 5

Ok now I am really lost!

import javax.swing.*;
 
 
//imported io file for the math method
import java.io.*;
//imported decimalformt for its format method
import java.text.DecimalFormat;
 
 
public class MCalculatorGUI2 extends javax.swing.JFrame
{
 
      /** Creating a new form MortgageCalGUI **/
      public MCalculatorGUI2()
      {
      int term = 0;
      double principal = 0;
      double rate = 0;
      double monthlyPayment = 0;
      double interest = 0;

            //call to method Components() to initilize the new from
            Components();
            
      }
 
      /** The Components() method is called within our MortgageCalGUI constructor to initilize our new MortgageCalGUI form **/
      private void Components()
      {
            //creating text fields
            txtfld_principal = new javax.swing.JTextField();
 
            //creating labels
            //principal label field
            label_principal = new javax.swing.JLabel();
            label_principal.setText("Principal (No comma's)");
            //term label field
            label_term = new javax.swing.JLabel();
            label_term.setText("Select your term year: ");
            
            //create a combo box for our terms
            bx_term = new javax.swing.JComboBox(terms);
            bx_term.setSelectedIndex(0);
            
            /*
            create a monthly label to be used for monthly payment output
            label_monthly = new javax.swing.JLabel();
            label_monthly.setText("$0.00");
            */
 
            //creating Button
            btn_calculate = new javax.swing.JButton();
            btn_calculate.setText("Calculate");
 
            //create out event handler for our combo box
            bx_term.addActionListener(new java.awt.event.ActionListener() {
                  public void actionPerformed(java.awt.event.ActionEvent evt) {
                        HandleComboBox(evt);
                  }
            });
            
            //create our event handler for our calculate button
            btn_calculate.addActionListener(new java.awt.event.ActionListener() {
                  public void actionPerformed(java.awt.event.ActionEvent evt) {
                        CalculationPerformed(evt);
                  }
            });            
            
            //create our "escape" route
            setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
            
            //create a new frame nameing it Mortgage Calculator
            JFrame frame = new JFrame("Mortgage Calculator");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //using our "escape" route for our new frame
            
            //set the layout of the window
            javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
            getContentPane().setLayout(layout);
            
            /*** HORIZONTAL POSITION LAYOUT ***/
            layout.setHorizontalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                  .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
 
                        /*** THE PRINCIPAL TEXT FIELD HORIZONTAL POSITION ***/
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                              .addGroup(layout.createSequentialGroup()
                                    .addComponent(txtfld_principal, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                    .addComponent(label_principal))
 
                        /* THE TERM LABEL FIELD HORIZONTOAL POSITION ***/
                              .addGroup(layout.createSequentialGroup()
                                    .addComponent(label_term))
 
                        /*** THE COMBO BOX HORIZONTAL POSITION ***/
                              .addGroup(layout.createSequentialGroup()
                                    .addComponent(bx_term))
 
                        /*** THE BUTTON HORIZONTAL POSITION ***/
                                    .addComponent(btn_calculate))
                                    .addComponent(temp_term))
 
                        .addContainerGap(27,Short.MAX_VALUE));
                        
            );
            
            layout.linkSize(javax.swing.SwingConstants.HORIZONTAL, new java.awt.Component[] {
                  btn_calculate,
                  bx_term,
                  txtfld_principal,
                  temp_term,
                  label_term }
            );
 
            /*** VERTICAL POSITION LAYOUT ***/
            layout.setVerticalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                  .addGroup(layout.createSequentialGroup()
                        .addContainerGap()
 
                        /*** THE PRINCIPAL TEXT FIELD VERTICAL POSITION ***/
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                              .addComponent(txtfld_principal, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                              .addComponent(label_principal))
 
                        /*** THER TERM LABEL FIELD VERTICAL POSITION ***/
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                              .addComponent(label_term))
 
                        /*** THE COMBO BOX VERTICAL POSITION ***/
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                              .addComponent(bx_term))
 
                        /*** THE CALCULATE BUTTON VERTICAL POSITION ***/
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                              .addComponent(btn_calculate))
 
                        .addContainerGap(21, Short.MAX_VALUE))
            );
            pack();
      }
      
      //HandleComboBox is called by the event handle for our combo box
      //Creates a temporary combo box to help set the arrays and to set the correct interest rates into the interest text field
      private void HandleComboBox(java.awt.event.ActionEvent evt)
      {
            //creating a temporary combo box
            //the source of our event is our combo box (bx_term)
            javax.swing.JComboBox temp_cb = (JComboBox)evt.getSource();
            
            //creating a temporary Sting to hold our selection from our combo box
            String temp_term = (String)temp_cb.getSelectedItem();
            txtfld_term.setText(temp_term + " years");
 
            //setting the index to our interest array
            int index = 0;
            switch((int)(Integer.parseInt(temp_term)))
            {
                  case 7 :
                        index = 0;
                        break;
                  case 15 :
                        index = 1;
                        break;
                  case 30 :
                        index = 2;
                        break;
            }
            //using the index for our interest array
            txtfld_interest.setText(interest[index]+"");
      }
            
      //CalculationPerformed is called by the event handler for out button
      //calculates the inputed values and then updates the monthly payment label
      private void CalculationPerformed(java.awt.event.ActionEvent evt)
      {
            
            //calculate payment based on inputed values
            final double temp_mthly = (temp_principal * (temp_interest/12)) / (1-Math.pow(1 + temp_interest/12,-(temp_term*12)));
            
            label_monthly.setText(DecimalPlaces.format(temp_mthly) + " Monthly");
      }      
 
      public static void main(String[] args)
      {
            java.awt.EventQueue.invokeLater(new Runnable() {
                  public void run() {
                        new MCalculatorGUI2().setVisible(true);
                  }
            });
      }
 
      /*** VARIABLES AND OBJECT DECLARATIONS ***/
      //labels
      private javax.swing.JLabel label_principal;
      private javax.swing.JLabel label_term;
      private javax.swing.JLabel label_interest;
      private javax.swing.JLabel label_monthly;
      private javax.swing.JLabel label_pymntschedule;
      
      //text fields
      private javax.swing.JTextField txtfld_principal;
      private javax.swing.JTextField txtfld_term;
      private javax.swing.JTextField txtfld_interest;
      private javax.swing.JTextField txtfld_monthly;
      private javax.swing.JTextField txtfld_pymntschedule;
      
      //arrays
      private String[] terms    = { "7", "15", "30" };
      private double[] interest = { 0.0535, 0.055, 0.0575 };
      
      //buttons
      private javax.swing.JComboBox bx_term;
      private javax.swing.JButton btn_calculate;
 
      //scroll pane
      private javax.swing.JScrollPane scroll_payments;
 
      //Delcaing object
      //declaring "decimalPlaces" as a new object type of DecimalFormat with the format of 0.00
      //this ensures any vaiables used by decimalPlaces has a "currancy" value of two decimal places
      private DecimalFormat DecimalPlaces = new DecimalFormat("$#,###,###.##");
}