Name: krT82822 Date: 05/19/99


When a java application is running holding a timer and an user
turns back the computer systemdate, the timer is only throwing
an event at the moment the original systemdate + delay is
reached.

5/19/99 kevin.ryan@eng -- received test case from user:

/*
Excuses for my late response on your request for a test case, but hereby
you receive a simple program that with some beter handwork will
demonstrate the problem.

The program shows the systemdate/time in a frame, every 1000
milliseconds later it will adjust the shown systemdate/time. If you turn
the systemclock (while the program still runs) forwards nothing shocking
happens, but when you turn the systemclock backwards the shown
systemdate/time will stop for as long as the systemclock reaches the
point it was turned back.

Hope this will demonstrate the problem properly for you.

Best Regards, Karel Mentink
*/

package nl.virgil.personal.karmen.timertest;

import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.*;

/**
 * Shows a window with the PC System Date to demonstrate the Timer
 * class behaviour.
 *
 * @version 1.00 19 May 1999
 * @author Dennis Brouwer
 */
public class TimerTest {

// To demonstrate the bug found adjust the System Date or Time
// FORWARD and BACKWARD. If you adjust Date or Time backwards, the
// timer is completely lost. This is possibly dangerous in certain
// applications. Please try for yourself.

        public static void main(String[] args) {

                // Creates a window to show PC System Date.
                JFrame timerFrame = new JFrame();

                // Sets the title and size of the window.
                timerFrame.setTitle("TimerTest");
                timerFrame.setSize(400,80);
                timerFrame.setResizable(false);

                timerFrame.addWindowListener(new WindowAdapter() {
                        public void windowClosing(WindowEvent e) {
                                System.exit(0);
                        }
                });

                // Shows the window on the screen.
                timerFrame.show();

                // Creates the pane containing the PC System Date.
                JPanel labelPane = new JPanel(new GridLayout(2,1));

                // Creates the label for the PC System Date.
                systemDateLabel = new JLabel("", SwingConstants.CENTER);
                systemDateLabel.setForeground(Color.black);

                // Creates the label for a text line to "play" with the System
                // Date.
                JLabel actionLabel = new JLabel("Please change PC System Date/Time forwards AND backwards", SwingConstants.CENTER);
                actionLabel.setForeground(Color.black);

                // Adds both labels to the window.
                labelPane.add(systemDateLabel);
                labelPane.add(actionLabel);

                // Add the pane to the window.
                Container contentPane = timerFrame.getContentPane();
                contentPane.add(labelPane);

                // Creates a timer event with one second interval to show the
                // PC System Date.
                Timer testTimer = new Timer(1000, new ActionListener() {
                        public void actionPerformed(ActionEvent e) {
                                // Gets system time and show in decent format.
                                actualDate = Calendar.getInstance();
                                systemDateLabel.setText(formatSystemDate());
                        }
                });

                // Start the timer.
                testTimer.start();
        }

        /**
         * Formats the System Date in a readable way.
         */
        private static String formatSystemDate() {
                // Creates the format for the system date.
                SimpleDateFormat formattedDate = new SimpleDateFormat ("dd MMMM yyyy hh:mm:ss");

                // Sets the system date in created format.
                String format = formattedDate.format(actualDate.getTime());

                return format;
        }

        private static JLabel systemDateLabel;
        private static Calendar actualDate;
(Review ID: 57846)
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