Scripting Assistance

Question

I am new to Java and looking for assistance with some basic scripting. The following 2 .java files are used to complete a mortgage calculation, and for some reason I am always ending up dividing by zero in my mortgage calculation equation (CalcEvent.java). This is called by MortgageGUI1.java. Any assistance anyone can provide would be very much appreciated.....
MortgageGUI1.java
* Program Name : Mortgage GUI 1
* Course : POS 407 - Week Two Assignment
* Original Version : 9 October 2004
* This Revision : 9 October 2004
* Programmer : Clifton Smith
* Purpose : This program will display a GUI which allows the
* user to input the loan amount, term of the loan,
* and the interest rate for a mortgage, upon which
* a monthly payment will be calculated and displayed.
* Version 1.0
/* Import the necessary Java APIs */
import java.awt.*;
import javax.swing.*;
/* Define the class */
public class MortgageGUI1 extends JFrame {
     CalcEvent mort = new CalcEvent(this);
     /* Set up Row 1 */
     JPanel row1 = new JPanel();
     JLabel principalLabel = new JLabel("Amount of the loan in whole dollars ", JLabel.RIGHT);
     JTextField principal = new JTextField(20);
     /* Set up Row 2 */
     JPanel row2 = new JPanel();
     JLabel termLabel = new JLabel("Length of the loan ", JLabel.RIGHT);
     JTextField term = new JTextField(20);
     /* Set up Row 3 */
     JPanel row3 = new JPanel();
     ButtonGroup option = new ButtonGroup();
     JCheckBox months = new JCheckBox("Months", false);
     JCheckBox years = new JCheckBox("Years", true);
     /* Set up Row 4 */
     JPanel row4 = new JPanel();
     JLabel interestLabel = new JLabel("Interest Rate ", JLabel.RIGHT);
     JTextField interest = new JTextField(20);
     /* Set up Row 5 */
     JPanel row5 = new JPanel();
     JButton calculate = new JButton("Calculate");
     JButton reset = new JButton("Reset");
     /* Set up Row 6 */
     JPanel row6 = new JPanel();
     JLabel paymentLabel = new JLabel("Amount of Monthly Payment ", JLabel.RIGHT);
     JTextField payment = new JTextField(20);
/* Subclass to draw the Java GUI */
public MortgageGUI1() {
     super("JAVA Mortgage Calculator");
     setSize(500, 300);
     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     GridLayout assemble = new GridLayout(6, 1, 10, 10);
     Container pane = getContentPane();
     pane.setLayout(assemble);
     /* Add Listeners */
     months.addItemListener(mort);
     years.addItemListener(mort);
     calculate.addActionListener(mort);
     reset.addActionListener(mort);
     /* Drawing Row 1 */
     GridLayout assemble1 = new GridLayout(1, 2, 10, 10);
     row1.setLayout(assemble1);
     //row1.setLayout(assemble1);
     row1.add(principalLabel);
     row1.add(principal);
     pane.add(row1);
     /* Drawing Row 2 */
     GridLayout assemble2 = new GridLayout(1, 2, 10, 10);
     row2.setLayout(assemble2);
     //row2.setLayout(assemble2);
     row2.add(termLabel);
     row2.add(term);
     pane.add(row2);
     /* Drawing Row 3 */
     FlowLayout assemble3 = new FlowLayout(FlowLayout.CENTER, 10, 10);
     option.add(months);
     option.add(years);
     row3.setLayout(assemble3);
     row3.add(months);
     row3.add(years);
     pane.add(row3);
     /* Drawing Row 4 */
     GridLayout assemble4 = new GridLayout(1, 2, 10, 10);
     row4.setLayout(assemble4);
     //row4.setLayout(assemble4);
     row4.add(interestLabel);
     row4.add(interest);
     pane.add(row4);
     /* Drawing Row 5 */
     FlowLayout assemble5 = new FlowLayout(FlowLayout.CENTER, 10, 10);
     option.add(calculate);
     option.add(reset);
     row5.setLayout(assemble5);
     row5.add(calculate);
     row5.add(reset);
     pane.add(row5);
     /* Drawing Row 6 */
     GridLayout assemble6 = new GridLayout(1, 2, 10, 10);
     row6.setLayout(assemble6);
     //row6.setLayout(assemble6);
     row6.add(paymentLabel);
     row6.add(payment);
     pane.add(row6);
     /* Displaying the Pane */
     setContentPane(pane);
     setVisible(true);
} /* End of MortgageGUI1 Subclass */
/* Define the main class */
     public static void main(String[] arguments) {
          MortgageGUI1 frame = new MortgageGUI1();
     } /* End of main class */
} /* End of MortgageGUI1 JFrame Subclass */
CalcEvent.java
* Program Name : CalcEvent
* Course : POS 407 - Week Two Assignment
* Original Version : 9 October 2004
* This Revision : 9 October 2004
* Programmer : Clifton Smith
* Purpose : This program will calculate the monthly payment
* and interpret start and reset actions from the
* MortgageGUI1 program.
* Version 1.0
/* Import the necessary Java APIs */
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import java.io.*;
import java.text.DecimalFormat;
/* Define the class */
public class CalcEvent implements ItemListener, ActionListener, Runnable {
/* Start the GUI */
MortgageGUI1 gui;
Thread calculating;
/* Define MortgageGUI1 as an attribute of CalcEvent */
public CalcEvent(MortgageGUI1 in) {
     gui = in;
/* Define the actions of the program */
public void actionPerformed(ActionEvent event) {
     String command = event.getActionCommand();
     if (command == "Calculate")
          startCalculating();
     if (command == "Reset")
          clearFields();
void startCalculating() {
     calculating = new Thread(this);
     calculating.start();
     gui.calculate.setEnabled(false);
     gui.reset.setEnabled(false);
     gui.months.setEnabled(false);
     gui.years.setEnabled(false);
void clearFields() {
     gui.principal.setText(null);
     gui.term.setText(null);
     gui.interest.setText(null);
     gui.payment.setText(null);
     gui.months.setEnabled(true);
     gui.years.setEnabled(true);
/* Define method to handle months vs. years selection */
int time;
int p;
int i;
public void itemStateChanged(ItemEvent event) {
     Object choice = event.getItem();
     if (choice == gui.years) {
          time = Integer.parseInt( gui.term.getText() );
          time = (time * 12);
     else {
          time = Integer.parseInt( gui.term.getText() );
String tempString;
public void run() {
Thread thisThread = Thread.currentThread();
     while (calculating == thisThread) {
          tempString = gui.principal.getText().trim ();
          p = (new Integer(tempString)).intValue();
          tempString = gui.interest.getText().trim ();
          i = (new Integer(tempString)).intValue();
          int rate = (1 + (i / 1200));
          //int rate = (1 + ((Integer.parseInt( gui.interest.getText() ) / 1200)));
          double mortgage = ((p * i * (Math.pow(rate,time))) / (1200 * (Math.pow(rate,time) - 1)));
          //double mortgage = (((Integer.parseInt( gui.principal.getText() )) * (Integer.parseInt( gui.interest.getText() )) * (Math.pow(rate,time)))/(1200 * (Math.pow(rate,time) - 1)));
          mortgage = (Math.rint(mortgage * 100)) / 100;
          //gui.payment.setText("$" + (tempString.valueOf(mortgage)));
          float monthlyPayment = (float)mortgage;
          gui.payment.setText("$" + monthlyPayment);
/* Reset GUI field values */
          gui.calculate.setEnabled(true);
          gui.reset.setEnabled(true);
          calculating = null;
}

Answer 1

I am always ending up dividing by zero...That's because you're working with int values, not floating point numbers.
        System.out.println(1 / 2); // 0
        System.out.println(1.0 / 2); // 0.5
SOME THINGS YOU SHOULD KNOW ABOUT FLOATING-POINT ARITHMETIC
What Every Computer Scientist Should Know About Floating-Point Arithmetic