Timers

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

interface Off { public void off (); }

class Timer extends Thread implements Off {
   Off guest = null;
   int amount, number=100;
   long time_at_start;
   
   public Timer (float a, Off g) {
      amount = (int)(a*10);
      guest = g;
      setPriority(7);
   }

   public String getTime () {
      long time_at_end = System.currentTimeMillis();
      return String.valueOf((double)(time_at_end - time_at_start)/1000.0);
   }
   
   public void off () { stop(); }
   
   public void run () {
      time_at_start = System.currentTimeMillis();
      try { sleep(number*amount); } catch (Exception e) {  }
      if (guest != null)  guest.off();    
   }
}

class Application extends Thread implements Off {
   Timer timer;
   TextArea text;
   int i=0;
   float time_amt;
   
   public Application (TextArea t, Choice cb) {
      text = t;
      time_amt = (new Float(cb.getSelectedItem())).floatValue();
      timer = new Timer(time_amt, this);
   }
   
   public void off () {
      text.append("Application "+String.valueOf(this)+" sent stop signal\n");
      stop();
   }

   public void run () {
      text.append("----------\n");
      text.append("Starting Application "+String.valueOf(this)+": 1 tick/second\n");
      text.append("Starting Timer for "+time_amt+" seconds\n");
      timer.start();
      for (i=1 ; i < 5 ; i++) {
         try {
            sleep(1000);
            text.append("Application: "+i+"\n");
         }
         catch (Exception e) {  text.append(String.valueOf(e));  }
      }
      text.append("Application Ending - turning timer off\n");
      text.append("Timer reports "+timer.getTime()+" seconds used\n");
      timer.off();
   }
}

public class TimerTest extends Applet implements ActionListener {
   Button startbut, resetbut;
   TextArea text;
   Choice cb;
   
   public void init () {
      setLayout(new BorderLayout(10,10));
      Panel p = new Panel();
      p.setLayout(new BorderLayout());
      p.add("North", new Label("Results"));
      p.add("Center", text = new TextArea(10,20));
      add("Center", p);
      Panel q = new Panel();
      q.setLayout(new GridLayout(1,4,10,10));
      q.add(startbut = new Button("Start"));
      q.add(resetbut = new Button("Reset"));
      q.add(new Label("Timer (secs)", Label.RIGHT));
      q.add(cb = new Choice());
      cb.addItem("0.5");
      cb.addItem("1.0");
      cb.addItem("1.5");
      cb.addItem("2.0");
      cb.addItem("2.5");
      cb.addItem("3.0");
      cb.addItem("3.5");
      cb.addItem("4.0");      
      cb.addItem("4.5");
      cb.addItem("5.0");      
      add("South", q);
      startbut.addActionListener(this);
      resetbut.addActionListener(this);
   }
   
   public void actionPerformed (ActionEvent e) {
      if (e.getSource() == startbut) run();
      else if (e.getSource() == resetbut) text.setText("");
   }
   
   public void run () {
      Application s = new Application(text, cb);
      s.start();
   }
}