Application freezes when "started"

Question

Here is the complete source for a countdown timer (i.e., a stopwatch).
The code compiles, but the program freezes whenever the user presses "start". The timer doesn't count down, either. The four levels of while loops in the `updateTextArea' function could very well contain the problem, but I'm not sure.
Also: The sloppy programming `updateTextArea' is a partial consequence of my not being allowed to use timekeeping utilities, other than a `Timer' object.
No "timeElapsed = someJavaUtility.timeNow - someJavaUtility.timeAtSomeReferenceTime" or anything like that.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class CountdownTimer extends JPanel {
        public static void main(String[] args) {
                JFrame f = new JFrame("Countdown Timer");
                 CountdownTimer content = new CountdownTimer();
                f.setContentPane(content);
                f.setSize(72 * 6, 72 * 3); // 6" x 3"
                f.setLocation(400, 100);
                f.setDefaultCloseOperation( JFrame.DISPOSE_ON_CLOSE );
                f.setVisible(true);
                f.setResizable(false);
        } // End main()
        JButton startButton, stopButton, resetButton, exitButton;
        JTextField display;
        JLabel message;
        JCheckBox hmToggle; // Toggles between hh:* and mmmm:* display.
        public CountdownTimer() {
                setBackground(Color.GRAY);
                setLayout( new FlowLayout(FlowLayout.LEFT, 10, 10) );
                TimeKeeper timeKeeper = new TimeKeeper();
                display = new JTextField("00:00:00.00");
                message = new JLabel("");
                add(display);
                add(message);
                add(timeKeeper);
                add(hmToggle);
         * Instances of this class hold the time remaining on the timer.
        private static class HMS {
                static final int
                        MINUTES = 1,  // Display time remaining as mmmm:ss
                        HOURS   = 10; // Display time remaining as hh:mm:ss
                int hours;
                int minutes;
                int seconds;
                // This variable holds TEN TIMES the number of milliseconds remaining.
                int msec;
        private class ConstructDisplay extends HMS {
                String displayHours = hours + ":" + minutes + ":" + seconds + "." + msec;
                String displayMinutes = minutes + ":" + seconds + "." + msec;
        private class Action implements ActionListener {
                public void actionPerformed(ActionEvent evt) { };
        private class TimeKeeper extends JPanel {
                        String timeEntered;             // Time entered in the display.
                        boolean minutesMode = false;    // Display mmmm:ss ?
                        HMS timeLeft;                   // Time remaining.
                        ConstructDisplay timerDisplay;  // Displays...
                        Timer timer;                    // Timer object.
                        public TimeKeeper() {
                                setLayout(new FlowLayout(FlowLayout.LEFT) );
                                startButton = new JButton("Start");
                                stopButton = new JButton("Stop");
                                resetButton = new JButton("Reset");
                                exitButton = new JButton("Exit");
                                hmToggle = new JCheckBox("Display Minutes and Seconds");
                                // Set up listening
                                startButton.addActionListener( new ActionListener() {
                                        public void actionPerformed(ActionEvent evt) {
                                                start();
                                stopButton.addActionListener(new Action() );
                                resetButton.addActionListener(new Action());
                                exitButton.addActionListener(new Action());
                                hmToggle.addActionListener(new Action());
                                // Add buttons to (sub-)panel
                                add(startButton);
                                add(stopButton);
                                add(resetButton);
                                add(exitButton);
                                ActionListener action = new ActionListener() {
                                        public void actionPerformed(ActionEvent evt) {
                                        Object source = evt.getSource();
                                               if(hmToggle == source) {
                                               // Monitors the state of the
                                               // checkbox.
                                               minutesMode = true;
                                        countDown();
                                timer = new Timer(10, action);
                                // On launch:
                                stopButton.setEnabled(false);
                                resetButton.setEnabled(false);
                        } // End constructor
                        public void paintComponent(Graphics g) {
                                super.paintComponent(g);
                         * Parse the display string, and start the timer.
                        private void start() {
                                if(timeLeft == null) {
                                        timeLeft = new HMS();
                                        timerDisplay = new ConstructDisplay();
                                // Disable interaction with the display while the
                                // timer is counting down.
                                display.setEditable(false);
                                timeEntered = display.getText();
                                // Fill the `timeLeft' record.
                                timeLeft.hours   = Integer.parseInt( timeEntered.substring(0, 1) );
                                timeLeft.minutes = Integer.parseInt( timeEntered.substring(3, 4) );
                                timeLeft.seconds = Integer.parseInt( timeEntered.substring(6, 7) );
                                timeLeft.msec    = Integer.parseInt( timeEntered.substring(9, 10) );
                                if(minutesMode) {
                                        timeLeft.minutes = Integer.parseInt( timeEntered.substring(0, 3) );
                                        timeLeft.seconds = Integer.parseInt( timeEntered.substring(5, 6) );
                                        timeLeft.msec    = Integer.parseInt( timeEntered.substring(8, 9) );
                                timer.start();
                        } // End start()
                         * Count down, 10 ms at a time. The display is updated
                         * based on the presentation selected by the user before clicking
                         * `start'.
                        private void countDown() {
                                updateTextArea(timeLeft, HMS.HOURS);
                                if(minutesMode) updateTextArea(timeLeft, HMS.MINUTES);
                                // Update a warning indicator (future release).
                         * Stops, but does not reset, the timer. Allows the user to
                         * pause (for breaks, for example).
                        private void stop() {
                                timer.stop();
                         * Resets the timer, which must be stopped before the
                         * display is reset.
                        private void reset() {
                                stop();
                                display.setText("00:00:00.00");
                                if(minutesMode) display.setText("0000:00.00");
                                timeLeft = null;
                         * Exits the program. (to avoid a possible namespace violation,
                         * the name `exit()' was not used).
                        private void exitTimer() {
                                System.exit(0);
                         * Called to alert the user that time is up.
                        private void timeIsUp() {
                                stop();
                                message.setText("Time's up!");
                         * Updates the display after each "tick" of the timer. The
                         * display used is dependent upon the user's preference.
                        private void updateTextArea(HMS timeLeft, int displayType) {
                                if(displayType == HMS.HOURS) {
                                while(timeLeft.hours >= 0) {
                                        while(timeLeft.minutes >= 0) {
                                                while(timeLeft.seconds >= 0) {
                                                        while(timeLeft.msec >= 0) {
                                                                if(timeLeft.hours == 0 && timeLeft.minutes == 0 && timeLeft.seconds == 0 && timeLeft.msec == 0)
                                                                        timeIsUp();
                                                                timeLeft.msec--;
                                                                display.setText(timerDisplay.displayHours);
                                                                if(timeLeft.msec == 0) {
                                                                        timeLeft.msec = 99;
                                                                        timeLeft.seconds--;
                                                                repaint();
                                                         } // End `ms' block
                                                         if(timeLeft.seconds == 0) {
                                                                timeLeft.seconds = 59;
                                                                timeLeft.minutes--;
                                                } // End `s' block
                                                if(timeLeft.minutes == 0) {
                                                      timeLeft.minutes = 59;
                                                      timeLeft.hours--;
                                        } // End `m' block
                                } // End `h' block
                                } // end if
                                // This is definitely cruft and will need to be cleaned up....
                                if(displayType == HMS.MINUTES) {
                                        while(timeLeft.minutes >= 0) {
                                                while(timeLeft.seconds >= 0) {
                                                        while(timeLeft.msec >= 0) {
                                                                if(timeLeft.minutes == 0 && timeLeft.seconds == 0 && timeLeft.msec == 0)
                                                                        timeIsUp();
                                                                timeLeft.msec--;
                                                                display.setText(timerDisplay.displayMinutes);
                                                                if(timeLeft.msec == 0) {
                                                                        timeLeft.msec = 99;
                                                                        timeLeft.seconds--;
                                                                repaint();
                                                         } // End `ms' block
                                                         if(timeLeft.seconds == 0) {
                                                                timeLeft.seconds = 59;
                                                                timeLeft.minutes--;
                                                } // End `s' block
                                        } // End `m' block
                                } // end if
                        } // End updateTextArea()
        } // End nested class TimeKeeper
}// End class CountdownTimer

Answer 1

I would suggest you rethink the approach to use a Swing Timer or a Thread for your countdown timer, i will post a short example of a
countdown timer using a swing timer. This countdown will update every second, but if you need to really accurate use a thread, all those nested whiles are scary, view Swing Timer api here:
http://java.sun.com/javase/6/docs/api/javax/swing/Timer.html
or Thread Here:
http://java.sun.com/javase/6/docs/api/java/lang/Thread.html
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
//Implement ActionListener in order to use a Swing Timer
public class SimpleTimer extends JFrame implements ActionListener{
     int time = 0;
     Timer timer; //Swing Timer
     JPanel display;
     public SimpleTimer(String s, int t){
          super(s);
          time= t;
          //Create a swing timer Timer(delay, ActionListener)
          timer = new Timer(1000, this);
                //Start the timer (This is the real advantage ofa swing timer hte start() and stop methods())
                //You may be using a button to do this or some other event but for simplicity i'm just starting it here
          timer.start();
          //display is used to show the time, i'm using paint but you could just as easily use a label or textbox etc...
          display = new JPanel(){
               public void paintComponent(Graphics g){
                    super.paintComponent(g);
                    g.drawString(time + "", 5, 20);
          getContentPane().add(display);
          setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
          setSize(300, 300);
          setVisible(true);
     //Is called by the Swing Timer
     public void actionPerformed(ActionEvent e){
          if (time == 0)
               timer.stop();
          else{
               time -= 1;
               repaint(); //Called because i used paintComponent(Graphics g), could be JLabel.setText(String s), blah blah blah
     public static void main(String[] args){
          SimpleTimer st = new SimpleTimer("Simple Timer", 100);
}