//  StopwatchKL.java  Copyright (c) 2005 Kari Laitinen

//  http://www.naturalprogramming.com

//  2005-06-21   File created.
//  2005-06-21   Last modification.

//  Solution to exercise 16-7

//  This program may sometimes print some numbers to the screen
//  after the stopwatch has been stopped. I guess that the reason
//  for that behavior is that in those cases the stopping command
//  is given in the middle of a printing operation.

import java.util.* ;

class  ThreadToMeasureTime  extends  Thread
{
   boolean  must_measure_time   =  true ;

   public void stop_this_thread()
   {
      must_measure_time  =  false ;
   }

   public void run()
   {
      long  start_time_ticks,  current_time_ticks ;
      long  elapsed_milliseconds ;

      System.out.print( "\n" ) ;

      start_time_ticks  =  System.currentTimeMillis() ;

      while ( must_measure_time  ==  true )
      {
         current_time_ticks  =  System.currentTimeMillis() ;

         elapsed_milliseconds  =  ( current_time_ticks  -  start_time_ticks ) ;

         System.out.printf( "\r  %d:%02d:%02d",
                            elapsed_milliseconds / 60000,   //  minutes
                            (( elapsed_milliseconds % 60000 ) / 1000 ),
                            (( elapsed_milliseconds % 1000 ) / 10 ) ) ;

         try
         {
            Thread.sleep( 10 ) ;  //  Sleeping 0.01 seconds
         }
         catch ( InterruptedException  caught_exception )
         {
         }
      }
   }
}

class StopwatchKL
{
   public static void main( String[] not_in_use )
   {
      Scanner keyboard = new Scanner( System.in ) ;

      ThreadToMeasureTime thread_to_measure_time  = 
                                       new ThreadToMeasureTime() ;

      System.out.print( "\n Press the Enter key to start the stopwatch. " ) ;

      String  any_string_from_keyboard  =  keyboard.nextLine() ;

      System.out.print( "\n Press the Enter key to stop the stopwatch.\n" ) ;

      thread_to_measure_time.start() ;

      any_string_from_keyboard  =  keyboard.nextLine() ;

      thread_to_measure_time.stop_this_thread() ;
   }
}