Java tutorial
/* From http://java.sun.com/docs/books/tutorial/index.html */ /* * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * -Redistribution of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * -Redistribution in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * Neither the name of Sun Microsystems, Inc. or the names of contributors may * be used to endorse or promote products derived from this software without * specific prior written permission. * * This software is provided "AS IS," without a warranty of any kind. ALL * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. * * You acknowledge that this software is not designed, licensed or intended * for use in the design, construction, operation or maintenance of any * nuclear facility. */ /* * InputVerificationDemo.java is a 1.4 example that * requires no other files. */ import java.awt.BorderLayout; import java.awt.Color; import java.awt.GridLayout; import java.awt.Toolkit; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.text.DecimalFormat; import java.text.NumberFormat; import java.text.ParseException; import javax.swing.BorderFactory; import javax.swing.InputVerifier; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextField; /** * 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(")"); } }