LoanAssistant.java

//package loanassistant;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.text.*;
public class LoanAssistant extends JFrame
{
JLabel balanceLabel = new JLabel();
JTextField balanceTextField = new JTextField();
JLabel interestLabel = new JLabel();
JTextField interestTextField = new JTextField();
JLabel monthsLabel = new JLabel();
JTextField monthsTextField = new JTextField();
JLabel paymentLabel = new JLabel();
JTextField paymentTextField = new JTextField();
JButton computeButton = new JButton();
JButton newLoanButton = new JButton();
JButton monthsButton = new JButton();
JButton paymentButton = new JButton();
JLabel analysisLabel = new JLabel();
JTextArea analysisTextArea = new JTextArea();
JButton exitButton = new JButton();
Font myFont = new Font("Arial", Font.PLAIN, 16);
Color lightYellow = new Color(255, 255, 128);
boolean computePayment;
public static void main(String args[])
/* Complete Project Code */

{
// create frame
new LoanAssistant().show();
}
public LoanAssistant()
{
// frame constructor
setTitle("Loan Assistant");
setResizable(false);
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent evt)
{
exitForm(evt);
}
});
getContentPane().setLayout(new GridBagLayout());
GridBagConstraints gridConstraints;
balanceLabel.setText("Loan Balance");
balanceLabel.setFont(myFont);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 0;
gridConstraints.gridy = 0;
gridConstraints.anchor = GridBagConstraints.WEST;
gridConstraints.insets = new Insets(10, 10, 0, 0);
getContentPane().add(balanceLabel, gridConstraints);
balanceTextField.setPreferredSize(new Dimension(100, 25));
balanceTextField.setHorizontalAlignment(SwingConstants.RIGHT);
balanceTextField.setFont(myFont);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 1;
gridConstraints.gridy = 0;

gridConstraints.insets = new Insets(10, 10, 0, 10);
getContentPane().add(balanceTextField, gridConstraints);
balanceTextField.addActionListener(new ActionListener ()
{
public void actionPerformed(ActionEvent e)
{
balanceTextFieldActionPerformed(e);
}
});
interestLabel.setText("Interest Rate");
interestLabel.setFont(myFont);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 0;
gridConstraints.gridy = 1;
gridConstraints.anchor = GridBagConstraints.WEST;
gridConstraints.insets = new Insets(10, 10, 0, 0);
getContentPane().add(interestLabel, gridConstraints);
interestTextField.setPreferredSize(new Dimension(100, 25));
interestTextField.setHorizontalAlignment(SwingConstants.RIGHT);
interestTextField.setFont(myFont);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 1;
gridConstraints.gridy = 1;
gridConstraints.insets = new Insets(10, 10, 0, 10);
getContentPane().add(interestTextField, gridConstraints);
interestTextField.addActionListener(new ActionListener ()
{
public void actionPerformed(ActionEvent e)
{
interestTextFieldActionPerformed(e);
}
});
monthsLabel.setText("Number of Payments");
monthsLabel.setFont(myFont);

gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 0;
gridConstraints.gridy = 2;
gridConstraints.anchor = GridBagConstraints.WEST;
gridConstraints.insets = new Insets(10, 10, 0, 0);
getContentPane().add(monthsLabel, gridConstraints);
monthsTextField.setPreferredSize(new Dimension(100, 25));
monthsTextField.setHorizontalAlignment(SwingConstants.RIGHT);
monthsTextField.setFont(myFont);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 1;
gridConstraints.gridy = 2;
gridConstraints.insets = new Insets(10, 10, 0, 10);
getContentPane().add(monthsTextField, gridConstraints);
monthsTextField.addActionListener(new ActionListener ()
{
public void actionPerformed(ActionEvent e)
{
monthsTextFieldActionPerformed(e);
}
});
paymentLabel.setText("Monthly Payment");
paymentLabel.setFont(myFont);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 0;
gridConstraints.gridy = 3;
gridConstraints.anchor = GridBagConstraints.WEST;
gridConstraints.insets = new Insets(10, 10, 0, 0);
getContentPane().add(paymentLabel, gridConstraints);
paymentTextField.setPreferredSize(new Dimension(100, 25));
paymentTextField.setHorizontalAlignment(SwingConstants.RIGHT);
paymentTextField.setFont(myFont);

gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 1;
gridConstraints.gridy = 3;
gridConstraints.insets = new Insets(10, 10, 0, 10);
getContentPane().add(paymentTextField, gridConstraints);
paymentTextField.addActionListener(new ActionListener ()
{
public void actionPerformed(ActionEvent e)
{
paymentTextFieldActionPerformed(e);
}
});
computeButton.setText("Compute Monthly Payment");
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 0;
gridConstraints.gridy = 4;
gridConstraints.gridwidth = 2;
gridConstraints.insets = new Insets(10, 0, 0, 0);
getContentPane().add(computeButton, gridConstraints);
computeButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
computeButtonActionPerformed(e);
}
});
newLoanButton.setText("New Loan Analysis");
newLoanButton.setEnabled(false);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 0;
gridConstraints.gridy = 5;
gridConstraints.gridwidth = 2;
gridConstraints.insets = new Insets(10, 0, 10, 0);
getContentPane().add(newLoanButton, gridConstraints);

newLoanButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
newLoanButtonActionPerformed(e);
}
});
monthsButton.setText("X");
monthsButton.setFocusable(false);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 2;
gridConstraints.gridy = 2;
gridConstraints.insets = new Insets(10, 0, 0, 0);
getContentPane().add(monthsButton, gridConstraints);
monthsButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
monthsButtonActionPerformed(e);
}
});
paymentButton.setText("X");
paymentButton.setFocusable(false);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 2;
gridConstraints.gridy = 3;
gridConstraints.insets = new Insets(10, 0, 0, 0);
getContentPane().add(paymentButton, gridConstraints);
paymentButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
paymentButtonActionPerformed(e);
}

});
analysisLabel.setText("Loan Analysis:");
analysisLabel.setFont(myFont);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 3;
gridConstraints.gridy = 0;
gridConstraints.anchor = GridBagConstraints.WEST;
gridConstraints.insets = new Insets(0, 10, 0, 0);
getContentPane().add(analysisLabel, gridConstraints);
analysisTextArea.setPreferredSize(new Dimension(250, 150));
analysisTextArea.setFocusable(false);
analysisTextArea.setBorder(BorderFactory.createLineBorder(Color.BLACK));
analysisTextArea.setFont(new Font("Courier New", Font.PLAIN, 14));
analysisTextArea.setEditable(false);
analysisTextArea.setBackground(Color.WHITE);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 3;
gridConstraints.gridy = 1;
gridConstraints.gridheight = 4;
gridConstraints.insets = new Insets(0, 10, 0, 10);
getContentPane().add(analysisTextArea, gridConstraints);
exitButton.setText("Exit");
exitButton.setFocusable(false);
gridConstraints = new GridBagConstraints();
gridConstraints.gridx = 3;
gridConstraints.gridy = 5;
getContentPane().add(exitButton, gridConstraints);
exitButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent e)
{
exitButtonActionPerformed(e);
}

});
pack();
Dimension screenSize =
Toolkit.getDefaultToolkit().getScreenSize();
setBounds((int) (0.5 * (screenSize.width - getWidth())), (int) (0.5 * (screenSize.height -
getHeight())), getWidth(), getHeight());
paymentButton.doClick();
}
private void exitForm(WindowEvent evt)
{
System.exit(0);
}
private void computeButtonActionPerformed(ActionEvent e)
{
double balance, interest, payment;
int months;
double monthlyInterest, multiplier;
double loanBalance, finalPayment;
if (validateDecimalNumber(balanceTextField))
{
balance =
Double.valueOf(balanceTextField.getText()).doubleValue();
}
else
{
	JOptionPane.showConfirmDialog(null, "Invalid or empty Loan Balance entry.\nPlease correct.", "Balance Input Error", JOptionPane.DEFAULT_OPTION,
			JOptionPane.INFORMATION_MESSAGE);
return;
}
if (validateDecimalNumber(interestTextField))
{
interest =
Double.valueOf(interestTextField.getText()).doubleValue();

}
else
{
JOptionPane.showConfirmDialog(null, "Invalid or empty Interest Rate entry.\nPlease correct.", "Interest Input Error", JOptionPane.DEFAULT_OPTION,
JOptionPane.INFORMATION_MESSAGE);
return;
}
monthlyInterest = interest / 1200;
if (computePayment)
{
// Compute loan payment
if (validateDecimalNumber(monthsTextField))
{
months =
Integer.valueOf(monthsTextField.getText()).intValue();
}
else
{
JOptionPane.showConfirmDialog(null, "Invalid or empty Number of Payments entry.\nPlease correct.", "Number of Payments Input Error",
JOptionPane.DEFAULT_OPTION, JOptionPane.INFORMATION_MESSAGE);
return;
}
if (interest == 0)
{
payment = balance / months;
}
else
{
multiplier = Math.pow(1 + monthlyInterest, months);
payment = balance * monthlyInterest * multiplier / (multiplier - 1);
}
paymentTextField.setText(new DecimalFormat("0.00").format(payment));
}
else

{
// Compute number of payments
if (validateDecimalNumber(paymentTextField))
{
payment =
Double.valueOf(paymentTextField.getText()).doubleValue();
if (payment <= (balance * monthlyInterest + 1.0))
{
if (JOptionPane.showConfirmDialog(null, "Minimum payment must be $" +
new DecimalFormat("0.00").format((int)(balance * monthlyInterest + 1.0)) + "\n" + "Do you want to use the minimum payment?", "Input Error", JOptionPane.YES_NO_OPTION,
JOptionPane.QUESTION_MESSAGE) == JOptionPane.YES_OPTION)
{
paymentTextField.setText(new DecimalFormat("0.00").format((int)(balance *
monthlyInterest + 1.0)));
payment =
Double.valueOf(paymentTextField.getText()).doubleValue();
}
else
{
paymentTextField.requestFocus();
return;
}
}
}
else
{
JOptionPane.showConfirmDialog(null, "Invalid or empty Monthly Payment entry.\nPlease correct.", "Payment Input Error", JOptionPane.DEFAULT_OPTION,
JOptionPane.INFORMATION_MESSAGE);
return;
}
if (interest == 0)
{
months = (int)(balance / payment);
}
else

{
months = (int)((Math.log(payment) - Math.log(payment - balance * monthlyInterest)) /
Math.log(1 + monthlyInterest));
}
monthsTextField.setText(String.valueOf(months));
}
// reset payment prior to analysis to fix at two decimals
payment =
Double.valueOf(paymentTextField.getText()).doubleValue();
// show analysis
analysisTextArea.setText("Loan Balance: $" + new
DecimalFormat("0.00").format(balance));
analysisTextArea.append("\n" + "Interest Rate: " + new
DecimalFormat("0.00").format(interest) + "%");
// process all but last payment
loanBalance = balance;
for (int paymentNumber = 1; paymentNumber <= months - 1; paymentNumber++)
{
loanBalance += loanBalance * monthlyInterest - payment;
}
// find final payment
finalPayment = loanBalance;
if (finalPayment > payment)
{
// apply one more payment
loanBalance += loanBalance * monthlyInterest - payment;
finalPayment = loanBalance;
months++;
monthsTextField.setText(String.valueOf(months));
}
analysisTextArea.append("\n\n" + String.valueOf(months - 1) + " Payments of $" + new
DecimalFormat("0.00").format(payment));
analysisTextArea.append("\n" + "Final Payment of: $" + new
DecimalFormat("0.00").format(finalPayment));
analysisTextArea.append("\n" + "Total Payments: $" + new
DecimalFormat("0.00").format((months - 1) * payment + finalPayment));
analysisTextArea.append("\n" + "Interest Paid $" + new

DecimalFormat("0.00").format((months - 1) * payment + finalPayment - balance));
computeButton.setEnabled(false);
newLoanButton.setEnabled(true);
newLoanButton.requestFocus();
}
private void newLoanButtonActionPerformed(ActionEvent e)
{
// clear computed value and analysis
if (computePayment)
{
paymentTextField.setText("");
}
else
{
monthsTextField.setText("");
}
analysisTextArea.setText("");
computeButton.setEnabled(true);
newLoanButton.setEnabled(false);
balanceTextField.requestFocus();
}
private void monthsButtonActionPerformed(ActionEvent e)
{
// will compute months
computePayment = false;
paymentButton.setVisible(true);
monthsButton.setVisible(false);
monthsTextField.setText("");
monthsTextField.setEditable(false);
monthsTextField.setBackground(lightYellow);
monthsTextField.setFocusable(false);
paymentTextField.setEditable(true);
paymentTextField.setBackground(Color.WHITE);
paymentTextField.setFocusable(true);

computeButton.setText("Compute Number of Payments");
balanceTextField.requestFocus();
}
private void paymentButtonActionPerformed(ActionEvent e)
{
// will compute payment
computePayment = true;
paymentButton.setVisible(false);
monthsButton.setVisible(true);
monthsTextField.setEditable(true);
monthsTextField.setBackground(Color.WHITE);
monthsTextField.setFocusable(true);
paymentTextField.setText("");
paymentTextField.setEditable(false);
paymentTextField.setBackground(lightYellow);
paymentTextField.setFocusable(false);
computeButton.setText("Compute Monthly Payment");
balanceTextField.requestFocus();
}
private void exitButtonActionPerformed(ActionEvent e)
{
System.exit(0);
}
private void balanceTextFieldActionPerformed(ActionEvent e)
{
balanceTextField.transferFocus();
}
private void interestTextFieldActionPerformed(ActionEvent e)
{
interestTextField.transferFocus();
}
private void monthsTextFieldActionPerformed(ActionEvent e)

{
monthsTextField.transferFocus();
}
private void paymentTextFieldActionPerformed(ActionEvent e)
{
paymentTextField.transferFocus();
}
private boolean validateDecimalNumber(JTextField tf)
{
// checks to see if text field contains
// valid decimal number with only digits and a single decimal point
String s = tf.getText().trim();
boolean hasDecimal = false;
boolean valid = true;
if (s.length() == 0)
{
valid = false;
}
else
{
for (int i = 0; i < s.length(); i++)
{
char c = s.charAt(i);
if (c >= '0' && c <= '9')
{
continue;
}
else if (c == '.' && !hasDecimal)
{
hasDecimal = true;
}
else
{
// invalid character found

valid = false;
}
}
}
tf.setText(s);
if (!valid)
{
tf.requestFocus();
}
return (valid);
}
}