Question

Write the program in Java (with a graphical user interface) and have it calculate and display the mortgage payment amount from user input of the amount of the mortgageand the user's selection from a menu of available mortgage loans:
•7 years at 5.35%
•15 years at 5.5%
•30 years at 5.75%
Use an array for the mortgage data for the different loans. Read the interest rates to fill the array from a sequential file. Display the mortgage payment amountfollowed by the loan balance and interest paid for each payment over the term of the loan. Add graphics in the form of a chart. Allow the user to loop back and enter anew amount and make a new selection or quit. Please insert comments in the program to document the program.

Answer 1

you need like this behind it

We will let L = loan, n = number of months for repayment, starting at
end of first month, r = percentage interest rate per year, (take r/12
as monthly rate). P = amount of repayment per month (starting at end
of first month).

If we consider the loan first, this would increase by a factor
(1 + r/1200) per month, so after n months the value of the loan would
have increased to L(1 + r/1200)^n

Now consider the repayments. These are $P per month, but the value of
the earlier repayments also increases at a compound rate (1 + r/1200).
Thus after the second repayment, the value of the repayments is:

P + P(1 + r/1200) and after three months it would be:
P + P(1 + r/1200) + P(1 + r/1200)^2 and after n months it would be:
P{1 + (1+r/1200) + (1+r/1200)^2 + ..... + (1+r/1200)^(n-1)}

This is a geometric series with n terms, first term = 1 and common
ratio (1+r/1200), so the sum of n terms is given by

P{(1+r/1200)^n - 1}/{(1+r/1200)-1)}
= P{(1+r/1200)^n - 1}/(r/1200)
= 1200P{(1+r/1200)^n - 1}/r

We must now equate the total repayments to total value of the loan,
and this gives:

1200P{(1+r/1200)^n - 1}/r = L(1+r/1200)^n

P = Lr(1+r/1200)^n/[1200{(1+r/1200)^n - 1}]

Example. Find the monthly repayments on a loan of $20,000 over 15
years at 12 percent per year compound interest.

Here we have n = 12*15 = 180 months, r = 12, and L = 20000.
We want to find P.

1+r/1200 = 1 + 12/1200 = 1.01 and the above formula becomes


P = {20000*12*1.01^180}/{1200*(1.01^180 - 1)}

= {20000*12*5.99}/{1200*(5.99 - 1)}

= 1437600/5988

= $240.08

Answer 2

//these packages need to be imported
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.JButton;
import javax.swing.JTextField;
import java.text.DecimalFormat;
//this is the calculator class
public class Calculator extends JPanel implements ActionListener
{

protected JComboBox MortCombo;
protected JLabel lblprincipal, lblinterestRate, lblTerm, lblmonthlyPayment;
protected JButton calculate, Clear;
protected JTextField principal, interestRate, Term, monthlyPayment;
protected TextArea MortTextField;
public Calculator()
{

String [] termString = {"7", "15", "30"};
String [] rateString = {"0.535", "0.055", "0.0575"};
//creates labels and fields
lblprincipal=new JLabel("Principal Amount:");
principal = new JTextField("",10);
lblinterestRate=new JLabel("Interest Rate:");
interestRate = new JTextField("",10);
lblTerm=new JLabel("Term:");
Term = new JTextField("",10);
lblmonthlyPayment=new JLabel("Monthly Payment:");
monthlyPayment = new JTextField("",10);
MortCombo=new JComboBox(comboItems);
MortTextField=new TextArea(10,120);
//The buttons are created here
calculate = new JButton("Calculate");
calculate.setActionCommand("GO");
Clear = new JButton("Clear");
Clear.setActionCommand("Clear");
//Added action for buttons here
calculate.addActionListener(this);
Clear.addActionListener(this);
add(lblprincipal);
add(principal);
add(lblinterestRate);
add(MortCombo);
add(lblTerm);
add(Term);
add(lblmonthlyPayment);
add(monthlyPayment);
add(calculate);
add(Clear);
add(MortTextField);
}
public void actionPerformed(ActionEvent e)
{

if ("GO".equals(e.getActionCommand()))
{

CalculateMortgage();
}
else
{

principal.setText("");
interestRate.setText("");
Term.setText("");
monthlyPayment.setText("");
}
}

//This is where the interest rate reads and shows it in the principal field
public void CalculateMortgage()
{

double dblprincipal=Double.parseDouble(principal.getText());
double dblinterestRate=Double.parseDouble((String)MortCombo.getSelectedItem());
int intTerm=Integer.parseInt(Term.getText());
DecimalFormat money = new DecimalFormat("$0.00");
double MonthlyPayment=0.0;
double InterestPayment=0.0;
double PrincipalBal=0.0;
double MIntRate=dblinterestRate/1200;
int MTerms=intTerm * 12;
//The formula for monthly payment here
MonthlyPayment=(dblprincipal * MIntRate) / (1-Math.pow((MIntRate+1),-MTerms));
//This is where monthly payments gets converted to decimal format
monthlyPayment.setText("" + (money.format(MonthlyPayment)));
MortTextField.append("Month No.ttMonthly PaymenttttLoan BalancetttInterest Paymentn");
MortTextField.append("1ttt" + MonthlyPayment + PrincipalBal + InterestPayment + "n");

for (int counter=1; counter < MTerms; counter++)
{

MortTextField.append((counter + 1) + "ttt" + MonthlyPayment + PrincipalBal + InterestPayment + "n");
}
}

private static void createAndShowGui()
{
//Jframe here
JFrame frame = new JFrame("Mortgage Calculator");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Calculator myCalculator = new Calculator();
myCalculator.setOpaque(true);
frame.setContentPane(myCalculator);
frame.pack();
frame.setVisible(true);
}

public static void main(String[] args)
{

javax.swing.SwingUtilities.invokeLater(
new Runnable()
{

public void run()
{
createAndShowGui();
}
}
);
}

Answer 3

import java.awt.*; //to create buttons, etc w/o actions
import java.awt.event.*; //to create an event or action
import javax.swing.*;
import javax.swing.JButton; //to create a button
import javax.swing.JTextField; //to create a text field
import java.text.DecimalFormat; //to import decimal format for money

//Class
public class MortgageText extends JPanel implements ActionListener
{
//Global Variable
protected JComboBox MortCombo;
protected JLabel lblprincipal, lblinterestRate, lblTerm, lblmonthlyPayment;
protected JButton calculate, Clear;
protected JTextField principal, interestRate, Term, monthlyPayment;
protected TextArea MortTextField;

public MortgageText()
{
String[] comboItems={"5.35","5.50","5.75","10.0"};

//creates labels and fields
lblprincipal=new JLabel("Principal Amount:");
principal = new JTextField("",10);
lblinterestRate=new JLabel("Interest Rate:");
interestRate = new JTextField("",10);
lblTerm=new JLabel("Term:");
Term = new JTextField("",10);
lblmonthlyPayment=new JLabel("Monthly Payment:");
monthlyPayment = new JTextField("",10);
MortCombo=new JComboBox(comboItems);
MortTextField=new TextArea(10,120);

//create buttons
calculate = new JButton("Calculate"); //button used to calculate mortgage payment
calculate.setActionCommand("GO");

Clear = new JButton("Clear"); //button used to clear data from the fields
Clear.setActionCommand("Clear");


//add action to button
calculate.addActionListener(this);
Clear.addActionListener(this);

add(lblprincipal);
add(principal);
add(lblinterestRate);
add(MortCombo);
add(lblTerm);
add(Term);
add(lblmonthlyPayment);
add(monthlyPayment);
add(calculate);
add(Clear);
add(MortTextField);

}
public void actionPerformed(ActionEvent e)
{
if ("GO".equals(e.getActionCommand()))
{
CalculateMortgage();
}
else
{
principal.setText("");
interestRate.setText("");
Term.setText("");
monthlyPayment.setText("");
}
}

// principal.setText(interestRate.getText()); --this will read the interestRate text field and copy it to the principal field

public void CalculateMortgage()
{
double dblprincipal=Double.parseDouble(principal.getText());
double dblinterestRate=Double.parseDouble((String)MortCombo.getSelectedItem());
int intTerm=Integer.parseInt(Term.getText());
DecimalFormat money = new DecimalFormat("$0.00");


double MonthlyPayment=0.0;
double InterestPayment=0.0;
double PrincipalBal=0.0;
double MIntRate=dblinterestRate/1200;
int MTerms=intTerm * 12;

//monthly payment formula
MonthlyPayment=(dblprincipal * MIntRate) / (1-Math.pow((MIntRate+1),-MTerms));

//converts Monthly Payment to decimal format
monthlyPayment.setText("" + (money.format(MonthlyPayment)));

MortTextField.append("Month No.ttMonthly PaymenttttLoan BalancetttInterest Paymentn");
MortTextField.append("1ttt" + MonthlyPayment + PrincipalBal + InterestPayment + "n");

//REMOVE "FOR" STATEMENT FOR WEEK 5 HOMEWORK
for (int counter=1; counter < MTerms; counter++)
{
MortTextField.append((counter + 1) + "ttt" + MonthlyPayment + PrincipalBal + InterestPayment + "n");
}

}

private static void createAndShowGui()
{
JFrame frame = new JFrame("Mortgage Calculator");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

MortgageText myCalculator = new MortgageText();
myCalculator.setOpaque(true);
frame.setContentPane(myCalculator);

frame.pack();
frame.setVisible(true);
}

public static void main(String[] args)
{
javax.swing.SwingUtilities.invokeLater(
new Runnable()
{
public void run()
{
createAndShowGui();
}
}

);

}



}
//Global Variable
protected JComboBox MortCombo;
protected JLabel lblprincipal, lblinterestRate, lblTerm, lblmonthlyPayment;
protected JButton calculate, Clear;
protected JTextField principal, interestRate, Term, monthlyPayment;
protected TextArea MortTextField;

public MortgageText()
{
String[] comboItems={"5.35","5.50","5.75","10.0"};

//creates labels and fields
lblprincipal=new JLabel("Principal Amount:");
principal = new JTextField("",10);
lblinterestRate=new JLabel("Interest Rate:");
interestRate = new JTextField("",10);
lblTerm=new JLabel("Term:");
Term = new JTextField("",10);
lblmonthlyPayment=new JLabel("Monthly Payment:");
monthlyPayment = new JTextField("",10);
MortCombo=new JComboBox(comboItems);
MortTextField=new TextArea(10,120);

//create buttons
calculate = new JButton("Calculate"); //button used to calculate mortgage payment
calculate.setActionCommand("GO");

Clear = new JButton("Clear"); //button used to clear data from the fields
Clear.setActionCommand("Clear");


//add action to button
calculate.addActionListener(this);
Clear.addActionListener(this);

add(lblprincipal);
add(principal);
add(lblinterestRate);
add(MortCombo);
add(lblTerm);
add(Term);
add(lblmonthlyPayment);
add(monthlyPayment);
add(calculate);
add(Clear);
add(MortTextField);

}
public void actionPerformed(ActionEvent e)
{
if ("GO".equals(e.getActionCommand()))
{
CalculateMortgage();
}
else
{
principal.setText("");
interestRate.setText("");
Term.setText("");
monthlyPayment.setText("");
}
}

// principal.setText(interestRate.getText()); --this will read the interestRate text field and copy it to the principal field

public void CalculateMortgage()
{
double dblprincipal=Double.parseDouble(principal.getText());
double dblinterestRate=Double.parseDouble((String)MortCombo.getSelectedItem());
int intTerm=Integer.parseInt(Term.getText());
DecimalFormat money = new DecimalFormat("$0.00");


double MonthlyPayment=0.0;
double InterestPayment=0.0;
double PrincipalBal=0.0;
double MIntRate=dblinterestRate/1200;
int MTerms=intTerm * 12;

//monthly payment formula
MonthlyPayment=(dblprincipal * MIntRate) / (1-Math.pow((MIntRate+1),-MTerms));

//converts Monthly Payment to decimal format
monthlyPayment.setText("" + (money.format(MonthlyPayment)));

MortTextField.append("Month No.ttMonthly PaymenttttLoan BalancetttInterest Paymentn");
MortTextField.append("1ttt" + MonthlyPayment + PrincipalBal + InterestPayment + "n");

//REMOVE "FOR" STATEMENT FOR WEEK 5 HOMEWORK
for (int counter=1; counter < MTerms; counter++)
{
MortTextField.append((counter + 1) + "ttt" + MonthlyPayment + PrincipalBal + InterestPayment + "n");
}

}

private static void createAndShowGui()
{
JFrame frame = new JFrame("Mortgage Calculator");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

MortgageText myCalculator = new MortgageText();
myCalculator.setOpaque(true);
frame.setContentPane(myCalculator);

frame.pack();
frame.setVisible(true);
}

public static void main(String[] args)
{
javax.swing.SwingUtilities.invokeLater(
new Runnable()
{
public void run()
{
createAndShowGui();
}
}

);

}



}

Answer 4

import java.io.*;
import java.text.DecimalFormat;

public class mortgagepaymentweek4 {
public static void main(String[] args) throws IOException {
int startNum, lineCtr, ctr, numMortgages;

// initalize the year array. This will be a 3 index array with the
// values
// 7, 15, and 30 at indexes 0, 1, and 2 respectively
int lastNum[] = { 7, 15, 30 };
int maxLineCtr = 25;
double initAmt, begYearAmt, endYearAmt, intThisYear, cumInterest;

// initialize the interest rates in the same manner as the years
double intRate[] = { 0.0535, 0.055, 0.0575 };
String nothing;
BufferedReader dataIn = new BufferedReader(new InputStreamReader(
System.in));
DecimalFormat twoDigits = new DecimalFormat("0.00");

// grab the number of mortgages we are comparing, in this case 3
numMortgages = lastNum.length;
lineCtr = 1;

// start a for loop in order to loop through our array of mortgages
for (int arrayIndex = 0; arrayIndex < numMortgages; arrayIndex++) {

// initialize amount and rates, we need to do this in each iteration
// of the array loop in order to not use old data where we shouldn't
initAmt = 200000.00;
// intRate = .0575;
begYearAmt = initAmt;
cumInterest = 0.00;

// compute the monthly payments using the standard mortgage
// formula
double i = intRate[arrayIndex] / 12;
int n = lastNum[arrayIndex] * 12;
double monthlyPayment = initAmt
* ((i * Math.pow((1 + i), n)) / (Math.pow((1 + i), n) - 1));

// print monthly payments
System.out
.println("----------------------------------------------------------------------------");
System.out.println(+ lastNum[arrayIndex]
+ " years at " + (intRate[arrayIndex] * 100) + "% with $"
+ twoDigits.format(monthlyPayment)
+ " monthly payment");
} // end for
// System.out.println("line ctr is " + line Ctr);
System.out
.println("----------------------------------------------------------------------------");
}// end main

}// end class

Answer 5

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.text.DecimalFormat;
import javax.swing.*;
import java.awt.image.BufferedImage;

public class MortgagePaymentCalculatorCR7 extends Frame implements ActionListener
{
//Initializing private global variables for the class
private Label lbl;
private Button submit;
private DecimalFormat calcPattern;
private Label lLoan ;
private TextField tLoan;
private Label lTerm;
private TextField tTerm;
private Label lInterestRate;
private TextField tInterestRate;
private Label fLoan;
private Label sLoan;
private Label thLoan;
private Label slbl;
private Button ssubmit;
private Label slLoan ;
private TextField stLoan;
private Label sfLoan;
private Label ssLoan;
private Label sthLoan;
private JRadioButton firstButton;
private JRadioButton secondButton;
private JRadioButton thirdButton;
private double loanInfo[][];
private JTable table;
private JTextArea output;
private Label displayText;
private JCheckBox displayButton;
private Label sdisplayText;
private JCheckBox sdisplayButton;
private Panel firstPanel;
private Panel secondPanel;
private Panel thirdPanel;
private Panel fourthPanel;
private Panel fifthPanel;
private Panel sixthPanel;
private Panel seventhPanel;
private DataInputStream istream;

public MortgagePaymentCalculatorCR7()
{
//Creating All needed panels to hold the different displays
firstPanel = new Panel();
secondPanel = new Panel();
thirdPanel = new Panel();
fourthPanel = new Panel();
fifthPanel = new Panel();
sixthPanel = new Panel();
seventhPanel = new Panel();
//Creating and Adding the Menu to the form
menuDisplay();
//Creating a WindowListener
addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(0);
}
});
//Filling Panel Displays with all of the needed Objects and adding panels to the form
add(selectDisplay(fifthPanel),BorderLayout.NORTH);
add(textDisplay(secondPanel),BorderLayout.NORTH);
//Creating the Layout for the chart image then drawing the chart
sixthPanel.setLayout(new FlowLayout());
//Creating and Initializing all of the variables for the chart image display
String mortgage = new String(" % Mortgage");
String mPayment = new String(" % Monthly Payment");
String iPayment = new String(" % Interest Payment");
String mHeading = new String(" Mortgage Chart");
Font hell2Font = new Font("Helvetica", Font.ITALIC, 14);
BufferedImage image=new BufferedImage(200,400,BufferedImage.TYPE_INT_ARGB);
JLabel label=new JLabel(new ImageIcon(image));
Graphics pen = image.getGraphics();
//Drawing a pie chart and a legend
//Creating all parts of the pie chart and legend in blue
pen.setColor(Color.blue);
pen.fillArc(10,50,100,100,45,270);
pen.fillRect(10,175,10,10);
//Creating all parts of the pie chart and legend in green
pen.setColor(Color.green);
pen.fillArc(10,50,100,100,340,65);
pen.fillRect(10,190,10,10);
//Creating all parts of the pie chart and legend in yellow
pen.setColor(Color.yellow);
pen.fillArc(20,57,100,100,315,25);
pen.fillRect(10,205,10,10);
//Writing the words in the legend
pen.setColor(Color.black);
pen.drawString(mortgage,20,185);
pen.drawString(mPayment,20,200);
pen.drawString(iPayment,20,215);
//Creating the Header of the Pie Chart image
pen.setFont(hell2Font);
pen.setColor(Color.blue);
pen.drawString(mHeading,10,10);
//clearing the pen
pen.dispose();
//Adding the drawn images to the display
sixthPanel.add(label);
seventhPanel.setLayout(new GridLayout(0,2,0,10));
seventhPanel.add(sixthPanel);

//Creating and initializing the text area with headings and making it uneditable
String header = "Loan Balance" +" "+ "Interest Paid" + "n";
output = new JTextArea(header,20,20);
output.setEnabled(false);
//Adding third panel to page and adding scroll bars to text area
thirdPanel.add(output, BorderLayout.CENTER);
thirdPanel.add(new JScrollPane(output));
seventhPanel.add(thirdPanel);
add(seventhPanel,BorderLayout.CENTER);
//Creating the array and filling it with data
CreateAndFillArray();
}
public void menuDisplay()
{
// Creating the menu for the application
MenuBar mnuBar = new MenuBar();
setMenuBar(mnuBar);
// Creating the File menu
Menu mnuFile = new Menu("File", true);
mnuBar.add(mnuFile);
MenuItem mnuFileExit = new MenuItem("Exit");
mnuFile.add(mnuFileExit);
// Creating the Edit menu and adding clear option
Menu mnuEdit = new Menu("Edit", true);
mnuBar.add(mnuEdit);
MenuItem mnuEditClear = new MenuItem("Clear");
mnuEdit.add(mnuEditClear);
//Creating the About menu
Menu mnuAbout = new Menu("About", true);
mnuBar.add(mnuAbout);
MenuItem mnuAboutCalculator = new MenuItem("About Mortgage Calculator");
mnuAbout.add(mnuAboutCalculator);
//Adding the ActionListener to each menu item
mnuFileExit.addActionListener(this);
mnuEditClear.addActionListener(this);
mnuAboutCalculator.addActionListener(this);
//Assigning an ActionCommand to each menu item
mnuFileExit.setActionCommand("Exit");
mnuEditClear.setActionCommand("Clear");
mnuAboutCalculator.setActionCommand("About");
}
public Panel textDisplay(Panel secondPanel)
{
//Creating sections to hold the fields, buttons, and labels for display
//Makes better layout for form items
firstPanel = new Panel();
displayText = new Label("");
displayButton = new JCheckBox("Available Mortgages");
lbl = new Label("");
lLoan = new Label("Mortgage Amount");
tLoan = new TextField(20);
lTerm = new Label("Mortgage Term in Years");
tTerm = new TextField(20);
lInterestRate = new Label("Interest Rate % per year");
tInterestRate =new TextField(20);
submit = new Button("Calculate Monthly Payment");
tLoan.setText("");
tTerm.setText("");
tInterestRate.setText("");
//Setting the layout for the panels of the labels and text fields
firstPanel.setLayout(new GridLayout(8,2,30,10));
firstPanel.add(displayButton);
firstPanel.add(displayText);
firstPanel.add(lLoan);
firstPanel.add(tLoan);
firstPanel.add(lTerm);
firstPanel.add(tTerm);
firstPanel.add(lInterestRate);
firstPanel.add(tInterestRate);
//Setting Action command and ActionListener for form submit button and display button
submit.setActionCommand("Calculate");
submit.addActionListener(this);
displayButton.setActionCommand("Select");
displayButton.addActionListener(this);
//Adding the form button and label that will display the Monthly payment results to the user to the form
firstPanel.add(submit);
firstPanel.add(lbl);
secondPanel.add(firstPanel);
return secondPanel;
}
public Panel selectDisplay(Panel fifthPanel)
{
//Creating sections to hold the fields, buttons, and labels for display
//Makes better layout for form items
fourthPanel = new Panel();
sdisplayText = new Label("");
sdisplayButton = new JCheckBox("Available Mortgages");
slbl = new Label("");
slLoan = new Label("Mortgage Amount");
stLoan = new TextField(20);
sfLoan = new Label("First Mortgage");
ssLoan = new Label("Second Mortgage");
sthLoan = new Label("Third Mortgage");
ssubmit = new Button("Calculate Monthly Payment");
stLoan.setText("");
//Creating and initializing radio buttons
firstButton = new JRadioButton("7 years at 5.35%");
firstButton.setSelected(true);
secondButton = new JRadioButton("15 years at 5.5%");
secondButton.setSelected(false);
thirdButton = new JRadioButton("30 years at 5.75%");
thirdButton.setSelected(false);
//Adding radio buttons to a group so they work together and only one can be selected at a time.
ButtonGroup bGroup = new ButtonGroup();
bGroup.add(firstButton);
bGroup.add(secondButton);
bGroup.add(thirdButton);
//Setting the layout for the panels of the labels and text fields
//firstPanel.removeAll();
fourthPanel.setLayout(new GridLayout(8,2,30,10));
fourthPanel.add(sdisplayButton);
fourthPanel.add(sdisplayText);
fourthPanel.add(slLoan);
fourthPanel.add(stLoan);
fourthPanel.add(sfLoan);
fourthPanel.add(firstButton);
fourthPanel.add(ssLoan);
fourthPanel.add(secondButton);
fourthPanel.add(sthLoan);
fourthPanel.add(thirdButton);
//Adding the form button and label that will display the Monthly payment results to the user to the form
fourthPanel.add(ssubmit);
fourthPanel.add(slbl);
//Setting Action command and ActionListener for form submit button
ssubmit.setActionCommand("MCalculate");
ssubmit.addActionListener(this);
sdisplayButton.setActionCommand("Select");
sdisplayButton.addActionListener(this);
fifthPanel.add(fourthPanel);
return fifthPanel;
}
public void actionPerformed(ActionEvent e)
{
//Catching user actions
String arg = e.getActionCommand();
//When Exit is selected close program
if(arg == "Exit")
System.exit(0);
//When Clear is selected clear all of the text fields and display label, then set focus on the mortgage field.
if(arg == "Clear")
{
stLoan.setText("");
firstButton.setSelected(true);
slbl.setText("");
stLoan.requestFocus();
tLoan.setText("");
tTerm.setText("");
tInterestRate.setText("");
lbl.setText("");
tLoan.requestFocus();
}
//When About is selected display message popup window
if(arg == "About")
{
String message = "Mortgage Calculator ver. 4.0nBarnett SoftwarenCopyright 2009nAll rights reserved";
JOptionPane.showMessageDialog(null, message,"About Mortgage Calculator", JOptionPane.INFORMATION_MESSAGE);
}
//When the checkbox is selected change the display
if (arg == "Select")
{
//When the checkbox is checked display the menu of mortgages
if(displayButton.isSelected())
{
//Adding the panel that contains the menu of mortgages to the form
add(fifthPanel,BorderLayout.NORTH);
remove(secondPanel);
displayButton.setSelected(false);
//reset all of the fields of the Panel that has just been added
stLoan.setText("");
firstButton.setSelected(true);
slbl.setText("");
stLoan.requestFocus();
}
else //When the checkbox is not checked display the text fields for free entry of Mortgages
{
//Adding the panel that contains the text fields for free entry
add(secondPanel,BorderLayout.NORTH);
remove(fifthPanel);
//Reset all of the fields of the panel that has just been added
tLoan.setText("");
tTerm.setText("");
tInterestRate.setText("");
lbl.setText("");
tLoan.requestFocus();
}
//Clearing the text area and resetting it
output.setText("");
output.setText(" Loan Balance" +" "+ "Interest Paid" + "n");
output.setRows(0);
output.setRows(20);
//Redrawing the screen
invalidate();
validate();
}
//When the Calculate button is selected calculate the user's input and display the monthly payment of the mortgage.
if(arg == "Calculate")
{
// Declaring all variables
int iLoan;
int years;
int months;
double loan;
double interest;
double interestRate;
double nPayments;
double pTemp;
double nTemp;
double monthlyPayment;

try
{
//Testing data received by user to see if it can be converted to numerical data
//If not then displaying a message to the user
loanInfo[3][3] = Double.parseDouble(tLoan.getText());
loanInfo[3][0] = Double.parseDouble(tTerm.getText());
loanInfo[3][1] = Double.parseDouble(tInterestRate.getText());
iLoan = 3;
//When data received by user contains numeric data checking to see if the data is greater than zero
//if not then displaying a message to the user
if(loanInfo[3][3] > 0 &&loanInfo[3][0] > 0 &&loanInfo[3][1] > 0)
{
years = (int)loanInfo[iLoan][0];
months = 12;
loan = loanInfo[3][3];
interest = loanInfo[iLoan][1]/100;
//Setting format of data for display
calcPattern = new DecimalFormat("########.##");
// Performing calculations on user input data to get the "monthly payment amount".
interestRate = interest/months;
nPayments = -(months * years);
pTemp = loan * interestRate;
nTemp = 1 - Math.pow((1 + interestRate), nPayments);
monthlyPayment = pTemp/nTemp;
loanInfo[iLoan][2] = monthlyPayment;
//Displaying the monthly payment amount to the user
lbl.setText(" $ " + calcPattern.format(monthlyPayment));
//Calling method for calculating loan balance and interest paid then displaying the results
CalculateLoanInt(iLoan,loanInfo);
}
else
{
//Message displayed to user if the input value is <= 0
lbl.setText("Input values greater than 0");
}
}
catch(Throwable exc)
{
//Message displayed to user if the input data is not a number
lbl.setText("Input numeric values only");
}
}
//When the Calculate button is selected calculate the user's input and display the monthly payment of the mortgage.
if(arg == "MCalculate")
{
// Declaring all variables
int iLoan;
int years;
int months;
double loan;
double interest;
double interestRate;
double nPayments;
double pTemp;
double nTemp;
double monthlyPayment;
try
{
//Testing data received by user to see if it can be converted to numerical data
//If not then displaying a message to the user
loanInfo[3][3] = Double.parseDouble(stLoan.getText());
//When data received by user contains numeric data checking to see if the data is greater than zero
//if not then displaying a message to the user
if(loanInfo[3][3] > 0)
{
iLoan = 0;
// Initializing variables with user input data
if(firstButton.isSelected())
iLoan = 0;
if(secondButton.isSelected())
iLoan = 1;
if(thirdButton.isSelected())
iLoan = 2;
years = (int)loanInfo[iLoan][0];
months = 12;
loan = loanInfo[3][3];
interest = loanInfo[iLoan][1]/100;
//Setting format of data for display
calcPattern = new DecimalFormat("########.##");
// Performing calculations on user input data to get the "monthly payment amount".
interestRate = interest/months;
nPayments = -(months * years);
pTemp = loan * interestRate;
nTemp = 1 - Math.pow((1 + interestRate), nPayments);
monthlyPayment = pTemp/nTemp;
loanInfo[iLoan][2] = monthlyPayment;
//Displaying the monthly payment amount to the user
slbl.setText(" $ " + calcPattern.format(monthlyPayment));
//Calling method for calculating loan balance and interest paid then displaying the results
CalculateLoanInt(iLoan,loanInfo);
}
else
{
//Message displayed to user if the input value is <= 0
slbl.setText("Input values greater than 0");
}
}
catch(Throwable exc)
{
//Message displayed to user if the input data is not a number
slbl.setText("Input numeric values only");
}
}
}
//Initializing variables to calculate loan balance and interest paid.(interest paid = P*r*t)
public double[][] CalculateLoanInt(int iLoan, double loanInfo[][])
{
double time;
double loanBalance;
double interestPaid;
double principalPaid;
double loanInterestInfo[][];
int iTerm;
int numPayments;
//Initializing variables for calculations
time = .083333; //time = 1/12
loanBalance = loanInfo[3][3];
interestPaid = loanInfo[3][3] * (loanInfo[iLoan][1]/100) * time;
numPayments = (int)loanInfo[iLoan][0] * 12;
loanInterestInfo = new double[numPayments][2];
iTerm = 0;
//Calculating the loan balance and interest paid for each monthly payment made over term of loan
//putting that information in a two dimensional array.
for(iTerm = 0; iTerm < numPayments; iTerm++)
{
interestPaid = loanBalance * (loanInfo[iLoan][1]/100) * time;
principalPaid = loanInfo[iLoan][2] - interestPaid;
loanBalance = loanBalance - principalPaid;
if (loanBalance < 0) loanBalance = 0;
loanInterestInfo[iTerm][0] = loanBalance;
loanInterestInfo[iTerm][1] = interestPaid;
}
//Setting format of data for display
calcPattern = new DecimalFormat("$ ##,###,###.##");
//Initializing variables and clearing text area and setting rows for text area based on loan
iTerm = 0;
output.setText("");
output.setText(" Loan Balance" +" "+ "Interest Paid" + "n");
output.setRows(numPayments);
//Displaying the loan balance and interest paid for each monthly payment made over term of loan
for(iTerm = 0; iTerm < numPayments; iTerm++)
{
output.append(" "+calcPattern.format(loanInterestInfo[iTerm][0])+" "+calcPattern.format(loanInterestInfo[iTerm][1])+"" + "n");
}
return loanInterestInfo;
}
public void CreateAndFillArray()
{
//Creating and initializing an array to hold mortgage data
int iRate;
loanInfo = new double[4][4];
// Filling array years for mortgage menu
loanInfo[0][0] = 7;
loanInfo[1][0] = 15;
loanInfo[2][0] = 30;
try
{
istream = new DataInputStream(new FileInputStream("interest.dat"));
}
catch(IOException e)
{
System.err.println("File not opened");
System.exit(1);
}
try
{
//Filling array with interest rates from a sequential file
for(iRate = 0; iRate < 3; iRate++)
{
loanInfo[iRate][1] = istream.readDouble();
}
}
catch(EOFException e2)
{
closeFile();
}
catch(IOException e3)
{
System.err.println("Error reading file");
System.exit(1);
}
}
public void closeFile()
{
try
{
istream.close();
System.exit(0);
}
catch(IOException e)
{
System.err.println("Error closing file");
System.exit(1);
}
}
public static void main(String[] args)
{
//Creating an instance of the Mortgage calculator
MortgagePaymentCalculatorCR7 mCal = new MortgagePaymentCalculatorCR7();
//Setting the mortgage calculator title, size and making it visible to the user
mCal.setTitle("Mortgage Calculator");
mCal.setSize(550,700);
mCal.setVisible(true);
}
}