/* * InputVerificationDemo.java is a 1.4 example that * requires no other files. */import java.util.Set;import java.util.HashSet;import java.awt.*;import java.awt.event.*;import javax.swing.*;import javax.swing.event.*;import javax.swing.text.*;import java.beans.PropertyChangeListener;import java.beans.PropertyChangeEvent;import java.text.*;/** * InputVerificationDemo.java is a 1.4 example that * requires no other files. * * Yet another mortgage calculator. * However, instead of using a formatted text field, * as shown in FormattedTextFieldDemo, this example * uses input verification to validate user input. */public class InputVerificationDemo extends JPanel {    //Default values    private static double DEFAULT_AMOUNT = 100000;    private static double DEFAULT_RATE = 7.5; //7.5%    private static int DEFAULT_PERIOD = 30;    //Labels to identify the text fields    private JLabel amountLabel;    private JLabel rateLabel;    private JLabel numPeriodsLabel;    private JLabel paymentLabel;    //Strings for the labels    private static String amountString = "Loan Amount (10,000-10,000,000): ";    private static String rateString = "APR (>= 0%): ";    private static String numPeriodsString = "Years (1-40): ";    private static String paymentString = "Monthly Payment: ";    //Text fields for data entry    private JTextField amountField;    private JTextField rateField;    private JTextField numPeriodsField;    private JTextField paymentField;    //Formats to format and parse numbers    private NumberFormat moneyFormat;    private NumberFormat percentFormat;    private DecimalFormat decimalFormat;    private DecimalFormat paymentFormat;    private MyVerifier verifier = new MyVerifier();    public InputVerificationDemo() {        super(new BorderLayout());        setUpFormats();        double payment = computePayment(DEFAULT_AMOUNT,                                        DEFAULT_RATE,                                        DEFAULT_PERIOD);        //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 JTextField(moneyFormat.format(DEFAULT_AMOUNT), 10);        amountField.setInputVerifier(verifier);        rateField = new JTextField(percentFormat.format(DEFAULT_RATE), 10);        rateField.setInputVerifier(verifier);        numPeriodsField = new JTextField(decimalFormat.format(DEFAULT_PERIOD), 10);        numPeriodsField.setInputVerifier(verifier);        paymentField = new JTextField(paymentFormat.format(payment), 10);        paymentField.setInputVerifier(verifier);        paymentField.setEditable(false);        //Remove this component from the focus cycle.        paymentField.setFocusable(false);        paymentField.setForeground(Color.red);        //Register an action listener to handle Return.        amountField.addActionListener(verifier);        rateField.addActionListener(verifier);        numPeriodsField.addActionListener(verifier);        //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);    }    class MyVerifier extends InputVerifier                     implements ActionListener {        double MIN_AMOUNT = 10000.0;        double MAX_AMOUNT = 10000000.0;        double MIN_RATE = 0.0;        int MIN_PERIOD = 1;        int MAX_PERIOD = 40;       public boolean shouldYieldFocus(JComponent input) {            boolean inputOK = verify(input);            makeItPretty(input);            updatePayment();            if (inputOK) {                return true;            } else {                Toolkit.getDefaultToolkit().beep();                return false;            }        }        protected void updatePayment() {            double amount = DEFAULT_AMOUNT;            double rate = DEFAULT_RATE;            int numPeriods = DEFAULT_PERIOD;            double payment = 0.0;            //Parse the values.            try {                amount = moneyFormat.parse(amountField.getText()).                                  doubleValue();            } catch (ParseException pe) {}            try {                rate = percentFormat.parse(rateField.getText()).                                     doubleValue();            } catch (ParseException pe) {}            try {                numPeriods = decimalFormat.parse(numPeriodsField.getText()).                                  intValue();            } catch (ParseException pe) {}            //Calculate the result and update the GUI.            payment = computePayment(amount, rate, numPeriods);            paymentField.setText(paymentFormat.format(payment));        }        //This method checks input, but should cause no side effects.        public boolean verify(JComponent input) {            return checkField(input, false);        }        protected void makeItPretty(JComponent input) {            checkField(input, true);        }        protected boolean checkField(JComponent input, boolean changeIt) {            if (input == amountField) {                return checkAmountField(changeIt);            } else if (input == rateField) {                return checkRateField(changeIt);            } else if (input == numPeriodsField) {                return checkNumPeriodsField(changeIt);            } else {                return true; //shouldn't happen            }        }        //Checks that the amount field is valid.  If it is valid,        //it returns true; otherwise, returns false.  If the        //change argument is true, this method reigns in the        //value if necessary and (even if not) sets it to the        //parsed number so that it looks good -- no letters,        //for example.        protected boolean checkAmountField(boolean change) {            boolean wasValid = true;            double amount = DEFAULT_AMOUNT;            //Parse the value.            try {                amount = moneyFormat.parse(amountField.getText()).                                  doubleValue();            } catch (ParseException pe) {                wasValid = false;            }            //Value was invalid.            if ((amount < MIN_AMOUNT) || (amount > MAX_AMOUNT)) {                wasValid = false;                if (change) {                    if (amount < MIN_AMOUNT) {                        amount = MIN_AMOUNT;                    } else { // amount is greater than MAX_AMOUNT                        amount = MAX_AMOUNT;                    }                }            }            //Whether value was valid or not, format it nicely.            if (change) {                amountField.setText(moneyFormat.format(amount));                amountField.selectAll();            }            return wasValid;        }        //Checks that the rate field is valid.  If it is valid,        //it returns true; otherwise, returns false.  If the        //change argument is true, this method reigns in the        //value if necessary and (even if not) sets it to the        //parsed number so that it looks good -- no letters,        //for example.        protected boolean checkRateField(boolean change) {            boolean wasValid = true;            double rate = DEFAULT_RATE;            //Parse the value.            try {                rate = percentFormat.parse(rateField.getText()).                                     doubleValue();            } catch (ParseException pe) {                wasValid = false;            }            //Value was invalid.            if (rate < MIN_RATE) {                wasValid = false;                if (change) {                    rate = MIN_RATE;                }            }            //Whether value was valid or not, format it nicely.            if (change) {                rateField.setText(percentFormat.format(rate));                rateField.selectAll();            }            return wasValid;        }        //Checks that the numPeriods field is valid.  If it is valid,        //it returns true; otherwise, returns false.  If the        //change argument is true, this method reigns in the        //value if necessary and (even if not) sets it to the        //parsed number so that it looks good -- no letters,        //for example.        protected boolean checkNumPeriodsField(boolean change) {            boolean wasValid = true;            int numPeriods = DEFAULT_PERIOD;            //Parse the value.            try {                numPeriods = decimalFormat.parse(numPeriodsField.getText()).                                  intValue();            } catch (ParseException pe) {                wasValid = false;            }            //Value was invalid.            if ((numPeriods < MIN_PERIOD) || (numPeriods > MAX_PERIOD)) {                wasValid = false;                if (change) {                    if (numPeriods < MIN_PERIOD) {                        numPeriods = MIN_PERIOD;                    } else { // numPeriods is greater than MAX_PERIOD                        numPeriods = MAX_PERIOD;                    }                }            }            //Whether value was valid or not, format it nicely.            if (change) {                numPeriodsField.setText(decimalFormat.format(numPeriods));                numPeriodsField.selectAll();            }            return wasValid;        }        public void actionPerformed(ActionEvent e) {            JTextField source = (JTextField)e.getSource();            shouldYieldFocus(source); //ignore return value            source.selectAll();        }    }    /**     * Create the GUI and show it.  For thread safety,     * this method should be invoked from the     * event-dispatching thread.     */    private static void createAndShowGUI() {        //Make sure we have nice window decorations.        JFrame.setDefaultLookAndFeelDecorated(true);        //Create and set up the window.        JFrame frame = new JFrame("InputVerificationDemo");        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        //Create and set up the content pane.        JComponent newContentPane = new InputVerificationDemo();        newContentPane.setOpaque(true); //content panes must be opaque        frame.setContentPane(newContentPane);        //Display the window.        frame.pack();        frame.setVisible(true);    }    public static void main(String[] args) {        //Schedule a job for the event-dispatching thread:        //creating and showing this application's GUI.        javax.swing.SwingUtilities.invokeLater(new Runnable() {            public void run() {                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 are used    //for both parsing input and formatting output.    private void setUpFormats() {        moneyFormat = (NumberFormat)NumberFormat.getNumberInstance();        percentFormat = NumberFormat.getNumberInstance();        percentFormat.setMinimumFractionDigits(3);        decimalFormat = (DecimalFormat)NumberFormat.getNumberInstance();        decimalFormat.setParseIntegerOnly(true);        paymentFormat = (DecimalFormat)NumberFormat.getNumberInstance();        paymentFormat.setMaximumFractionDigits(2);        paymentFormat.setNegativePrefix("(");        paymentFormat.setNegativeSuffix(")");    }}