// This code demonstrates the implementation of the depricated suspend() and
// resume() methods of class Thread. To make it possible, the StopWatch
// thread should be implemented as Runnable rather than extending the class
// Thread. 

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

public class StopWatch extends JApplet implements ActionListener
{
  private JButton suspendB = new JButton("Suspend");
  private JButton resumeB = new JButton("Resume");
  private JLabel display = new JLabel("", JLabel.CENTER);
  private StopWatchThread stopWatch;

  public void init()
  {
    Container pane = getContentPane();        // build GUI
    pane.setLayout(new BorderLayout());
    pane.setBackground(Color.orange);
    display.setFont(new Font("Monospace", Font.BOLD, 24));
    pane.add(display, BorderLayout.CENTER);
    JPanel controlPanel = new JPanel();
    controlPanel.add(suspendB);
    controlPanel.add(resumeB);
    controlPanel.setBackground(Color.lightGray);
    pane.add(controlPanel, BorderLayout.SOUTH);

    suspendB.addActionListener(this);         // button listeners
    resumeB.addActionListener(this);
    stopWatch = new StopWatchThread(display); // create and start stopwatch
  }

  public void actionPerformed(ActionEvent e)  // stopwatch control center
  {
    if (e.getSource() == suspendB)
      stopWatch.suspend();
    else if (e.getSource() == resumeB)
      stopWatch.resume();
  }     
}

class StopWatchThread implements Runnable     // stopwatch thread 
{
  private boolean suspended = false;          // stopwatch state
  private JLabel display;                     // applet's time display

  public StopWatchThread(JLabel l)            // thread constructor
  {
    display = l;                              // ref. to applet's display
    (new Thread(this)).start();               // create and start thread
  }

  public void run()
  {
    while(true)
    {
      Calendar calendar = Calendar.getInstance();      // get time instance
      int hours = calendar.get(Calendar.HOUR_OF_DAY);
      int minutes =  calendar.get(Calendar.MINUTE);
      int seconds = calendar.get(Calendar.SECOND);
      display.setText(hours + ":" +                    // update clock display
        ((minutes > 9) ? minutes : "0" + minutes) + ":" +
        ((seconds > 9) ? seconds : "0" + seconds));

      try                                      // wait 1 sec for the       
      {                                        // next update
        Thread.sleep(1000);
        waitIfSuspended();                     // proceed if not suspended
      }
      catch(InterruptedException e){}
    }
  }

  public synchronized void suspend()           
  {                                         
    suspended = true;
  }

  public synchronized void resume()
  {
    if (suspended)
    {
      suspended = false;
      notifyAll();                             // move the thread back to 
    }                                          // the runnable state
  }

  private synchronized void waitIfSuspended() throws InterruptedException
  {
    while (suspended)                          // moving the thread to
      wait();                                  // the blocked state
  } 
}