Mega Code Archive
It implements a mortgage calculator that uses four JFormattedTextFields
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import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.text.NumberFormat;
import javax.swing.BorderFactory;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
/**
* FormattedTextFieldDemo.java requires no other files.
*
* It implements a mortgage calculator that uses four JFormattedTextFields.
*/
public class FormattedTextFieldDemo extends JPanel implements
PropertyChangeListener {
// Values for the fields
private double amount = 100000;
private double rate = 7.5; // 7.5%
private int numPeriods = 30;
// Labels to identify the fields
private JLabel amountLabel;
private JLabel rateLabel;
private JLabel numPeriodsLabel;
private JLabel paymentLabel;
// Strings for the labels
private static String amountString = "Loan Amount: ";
private static String rateString = "APR (%): ";
private static String numPeriodsString = "Years: ";
private static String paymentString = "Monthly Payment: ";
// Fields for data entry
private JFormattedTextField amountField;
private JFormattedTextField rateField;
private JFormattedTextField numPeriodsField;
private JFormattedTextField paymentField;
// Formats to format and parse numbers
private NumberFormat amountFormat;
private NumberFormat percentFormat;
private NumberFormat paymentFormat;
public FormattedTextFieldDemo() {
super(new BorderLayout());
setUpFormats();
double payment = computePayment(amount, rate, numPeriods);
// Create the labels.
amountLabel = new JLabel(amountString);
rateLabel = new JLabel(rateString);
numPeriodsLabel = new JLabel(numPeriodsString);
paymentLabel = new JLabel(paymentString);
// Create the text fields and set them up.
amountField = new JFormattedTextField(amountFormat);
amountField.setValue(new Double(amount));
amountField.setColumns(10);
amountField.addPropertyChangeListener("value", this);
rateField = new JFormattedTextField(percentFormat);
rateField.setValue(new Double(rate));
rateField.setColumns(10);
rateField.addPropertyChangeListener("value", this);
numPeriodsField = new JFormattedTextField();
numPeriodsField.setValue(new Integer(numPeriods));
numPeriodsField.setColumns(10);
numPeriodsField.addPropertyChangeListener("value", this);
paymentField = new JFormattedTextField(paymentFormat);
paymentField.setValue(new Double(payment));
paymentField.setColumns(10);
paymentField.setEditable(false);
paymentField.setForeground(Color.red);
// Tell accessibility tools about label/textfield pairs.
amountLabel.setLabelFor(amountField);
rateLabel.setLabelFor(rateField);
numPeriodsLabel.setLabelFor(numPeriodsField);
paymentLabel.setLabelFor(paymentField);
// Lay out the labels in a panel.
JPanel labelPane = new JPanel(new GridLayout(0, 1));
labelPane.add(amountLabel);
labelPane.add(rateLabel);
labelPane.add(numPeriodsLabel);
labelPane.add(paymentLabel);
// Layout the text fields in a panel.
JPanel fieldPane = new JPanel(new GridLayout(0, 1));
fieldPane.add(amountField);
fieldPane.add(rateField);
fieldPane.add(numPeriodsField);
fieldPane.add(paymentField);
// Put the panels in this panel, labels on left,
// text fields on right.
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
add(labelPane, BorderLayout.CENTER);
add(fieldPane, BorderLayout.LINE_END);
}
/** Called when a field's "value" property changes. */
public void propertyChange(PropertyChangeEvent e) {
Object source = e.getSource();
if (source == amountField) {
amount = ((Number) amountField.getValue()).doubleValue();
} else if (source == rateField) {
rate = ((Number) rateField.getValue()).doubleValue();
} else if (source == numPeriodsField) {
numPeriods = ((Number) numPeriodsField.getValue()).intValue();
}
double payment = computePayment(amount, rate, numPeriods);
paymentField.setValue(new Double(payment));
}
/**
* Create the GUI and show it. For thread safety, this method should be
* invoked from the event dispatch thread.
*/
private static void createAndShowGUI() {
// Create and set up the window.
JFrame frame = new JFrame("FormattedTextFieldDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Add contents to the window.
frame.add(new FormattedTextFieldDemo());
// Display the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
// Schedule a job for the event dispatch thread:
// creating and showing this application's GUI.
SwingUtilities.invokeLater(new Runnable() {
public void run() {
// Turn off metal's use of bold fonts
UIManager.put("swing.boldMetal", Boolean.FALSE);
createAndShowGUI();
}
});
}
// Compute the monthly payment based on the loan amount,
// APR, and length of loan.
double computePayment(double loanAmt, double rate, int numPeriods) {
double I, partial1, denominator, answer;
numPeriods *= 12; // get number of months
if (rate > 0.01) {
I = rate / 100.0 / 12.0; // get monthly rate from annual
partial1 = Math.pow((1 + I), (0.0 - numPeriods));
denominator = (1 - partial1) / I;
} else { // rate ~= 0
denominator = numPeriods;
}
answer = (-1 * loanAmt) / denominator;
return answer;
}
// Create and set up number formats. These objects also
// parse numbers input by user.
private void setUpFormats() {
amountFormat = NumberFormat.getNumberInstance();
percentFormat = NumberFormat.getNumberInstance();
percentFormat.setMinimumFractionDigits(3);
paymentFormat = NumberFormat.getCurrencyInstance();
}
}
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