An applet that counts down from a specified time : Timer « Swing JFC « Java

An applet that counts down from a specified time

 * Copyright (c) 2004 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 3nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose,
 * including teaching and use in open-source projects.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book, 
 * please visit

import java.applet.AudioClip;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.Image;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.text.NumberFormat;

import javax.swing.ImageIcon;
import javax.swing.JApplet;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
import javax.swing.Timer;

 * An applet that counts down from a specified time. When it reaches 00:00, it
 * optionally plays a sound and optionally moves the browser to a new page.
 * Place the mouse over the applet to pause the count; move it off to resume.
 * This class demonstrates most applet methods and features.
public class Countdown extends JApplet implements ActionListener, MouseListener {
  long remaining; // How many milliseconds remain in the countdown.

  long lastUpdate; // When count was last updated

  JLabel label; // Displays the count

  Timer timer; // Updates the count every second

  NumberFormat format; // Format minutes:seconds with leading zeros

  Image image; // Image to display along with the time

  AudioClip sound; // Sound to play when we reach 00:00

  // Called when the applet is first loaded
  public void init() {
    // Figure out how long to count for by reading the "minutes" parameter
    // defined in a <param> tag inside the <applet> tag. Convert to ms.
    String minutes = getParameter("minutes");
    if (minutes != null)
      remaining = Integer.parseInt(minutes) * 60000;
      remaining = 600000; // 10 minutes by default

    // Create a JLabel to display remaining time, and set some properties.
    label = new JLabel();
    label.setOpaque(true); // So label draws the background color

    // Read some parameters for this JLabel object
    String font = getParameter("font");
    String foreground = getParameter("foreground");
    String background = getParameter("background");
    String imageURL = getParameter("image");

    // Set label properties based on those parameters
    if (font != null)
    if (foreground != null)
    if (background != null)
    if (imageURL != null) {
      // Load the image, and save it so we can release it later
      image = getImage(getDocumentBase(), imageURL);
      // Now display the image in the JLabel.
      label.setIcon(new ImageIcon(image));

    // Now add the label to the applet. Like JFrame and JDialog, JApplet
    // has a content pane that you add children to
    getContentPane().add(label, BorderLayout.CENTER);

    // Get an optional AudioClip to play when the count expires
    String soundURL = getParameter("sound");
    if (soundURL != null)
      sound = getAudioClip(getDocumentBase(), soundURL);

    // Obtain a NumberFormat object to convert number of minutes and
    // seconds to strings. Set it up to produce a leading 0 if necessary
    format = NumberFormat.getNumberInstance();
    format.setMinimumIntegerDigits(2); // pad with 0 if necessary

    // Specify a MouseListener to handle mouse events in the applet.
    // Note that the applet implements this interface itself

    // Create a timer to call the actionPerformed() method immediately,
    // and then every 1000 milliseconds. Note we don't start the timer yet.
    timer = new Timer(1000, this);
    timer.setInitialDelay(0); // First timer is immediate.

  // Free up any resources we hold; called when the applet is done
  public void destroy() {
    if (image != null)

  // The browser calls this to start the applet running
  // The resume() method is defined below.
  public void start() {
  } // Start displaying updates

  // The browser calls this to stop the applet. It may be restarted later.
  // The pause() method is defined below
  public void stop() {
  } // Stop displaying updates

  // Return information about the applet
  public String getAppletInfo() {
    return "Countdown applet Copyright (c) 2003 by David Flanagan";

  // Return information about the applet parameters
  public String[][] getParameterInfo() {
    return parameterInfo;

  // This is the parameter information. One array of strings for each
  // parameter. The elements are parameter name, type, and description.
  static String[][] parameterInfo = {
      { "minutes", "number", "time, in minutes, to countdown from" },
      { "font", "font", "optional font for the time display" },
      { "foreground", "color", "optional foreground color for the time" },
      { "background", "color", "optional background color" },
      { "image", "image URL", "optional image to display next to countdown" },
      { "sound", "sound URL", "optional sound to play when we reach 00:00" },
      { "newpage", "document URL", "URL to load when timer expires" }, };

  // Start or resume the countdown
  void resume() {
    // Restore the time we're counting down from and restart the timer.
    lastUpdate = System.currentTimeMillis();
    timer.start(); // Start the timer

  // Pause the countdown
  void pause() {
    // Subtract elapsed time from the remaining time and stop timing
    long now = System.currentTimeMillis();
    remaining -= (now - lastUpdate);
    timer.stop(); // Stop the timer

  // Update the displayed time. This method is called from actionPerformed()
  // which is itself invoked by the timer.
  void updateDisplay() {
    long now = System.currentTimeMillis(); // current time in ms
    long elapsed = now - lastUpdate; // ms elapsed since last update
    remaining -= elapsed; // adjust remaining time
    lastUpdate = now; // remember this update time

    // Convert remaining milliseconds to mm:ss format and display
    if (remaining < 0)
      remaining = 0;
    int minutes = (int) (remaining / 60000);
    int seconds = (int) ((remaining % 60000) / 1000);
    label.setText(format.format(minutes) + ":" + format.format(seconds));

    // If we've completed the countdown beep and display new page
    if (remaining == 0) {
      // Stop updating now.
      // If we have an alarm sound clip, play it now.
      if (sound != null);
      // If there is a newpage URL specified, make the browser
      // load that page now.
      String newpage = getParameter("newpage");
      if (newpage != null) {
        try {
          URL url = new URL(getDocumentBase(), newpage);
        } catch (MalformedURLException ex) {

  // This method implements the ActionListener interface.
  // It is invoked once a second by the Timer object
  // and updates the JLabel to display minutes and seconds remaining.
  public void actionPerformed(ActionEvent e) {

  // The methods below implement the MouseListener interface. We use
  // two of them to pause the countdown when the mouse hovers over the timer.
  // Note that we also display a message in the statusline
  public void mouseEntered(MouseEvent e) {
    pause(); // pause countdown
    showStatus("Paused"); // display statusline message

  public void mouseExited(MouseEvent e) {
    resume(); // resume countdown
    showStatus(""); // clear statusline

  // These MouseListener methods are unused.
  public void mouseClicked(MouseEvent e) {

  public void mousePressed(MouseEvent e) {

  public void mouseReleased(MouseEvent e) {


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