Java tutorial
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 java.text.ParseException; 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; import javax.swing.text.DefaultFormatterFactory; import javax.swing.text.NumberFormatter; /** * FormatterFactoryDemo.java requires no other files. */ public class FormatterFactoryDemo extends JPanel implements PropertyChangeListener { // Values for the text fields private double amount = 100000; private double rate = .075; // 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 amountDisplayFormat; private NumberFormat amountEditFormat; private NumberFormat percentDisplayFormat; private NumberFormat percentEditFormat; private NumberFormat paymentFormat; public FormatterFactoryDemo() { 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(new DefaultFormatterFactory(new NumberFormatter(amountDisplayFormat), new NumberFormatter(amountDisplayFormat), new NumberFormatter(amountEditFormat))); amountField.setValue(new Double(amount)); amountField.setColumns(10); amountField.addPropertyChangeListener("value", this); NumberFormatter percentEditFormatter = new NumberFormatter(percentEditFormat) { public String valueToString(Object o) throws ParseException { Number number = (Number) o; if (number != null) { double d = number.doubleValue() * 100.0; number = new Double(d); } return super.valueToString(number); } public Object stringToValue(String s) throws ParseException { Number number = (Number) super.stringToValue(s); if (number != null) { double d = number.doubleValue() / 100.0; number = new Double(d); } return number; } }; rateField = new JFormattedTextField(new DefaultFormatterFactory(new NumberFormatter(percentDisplayFormat), new NumberFormatter(percentDisplayFormat), percentEditFormatter)); 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("FormatterFactoryDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Add contents to the window. frame.add(new FormatterFactoryDemo()); // 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 > 0.001) { I = rate / 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() { amountDisplayFormat = NumberFormat.getCurrencyInstance(); amountDisplayFormat.setMinimumFractionDigits(0); amountEditFormat = NumberFormat.getNumberInstance(); percentDisplayFormat = NumberFormat.getPercentInstance(); percentDisplayFormat.setMinimumFractionDigits(2); percentEditFormat = NumberFormat.getNumberInstance(); percentEditFormat.setMinimumFractionDigits(2); paymentFormat = NumberFormat.getCurrencyInstance(); } }