1	/** StopWatch.java
    2	   A stopwatch accumulates time when it is running. You can
    3	   repeatedly start and stop the stopwatch. You can use a
    4	   stopwatch to measure the running time of a program.	*/
    6	public class StopWatch
    7	{
    8	   /**
    9	      Constructs a stopwatch that is in the stopped state
   10	      and has no time accumulated.   */
   12	   public StopWatch()
   13	   {
   14	      reset();
   15	   }
   17	   /**
   18	      Starts the stopwatch. Time starts accumulating now. */
   20	   public void start()
   21	   {
   22	      if (isRunning) return;
   23	      isRunning = true;
   24	      startTime = System.currentTimeMillis();
   25	   }
   27	   /**
   28	      Stops the stopwatch. Time stops accumulating and is
   29	      is added to the elapsed time.*/
   31	   public void stop()
   32	   {
   33	      if (!isRunning) return;
   34	      isRunning = false;
   35	      long endTime = System.currentTimeMillis();
   36	      elapsedTime = elapsedTime + endTime - startTime;
   37	   }
   39	   /**
   40	      Returns the total elapsed time.
   41	      @return the total elapsed time*/
   43	   public long getElapsedTime()
   44	   {
   45	      if (isRunning)
   46	      {
   47	         long endTime = System.currentTimeMillis();
   48	         return elapsedTime + endTime - startTime;
   49	      }
   50	      else
   51	         return elapsedTime;
   52	   }
   54	   /**
   55	      Stops the watch and resets the elapsed time to 0.*/
   57	   public void reset()
   58	   {
   59	      elapsedTime = 0;
   60	      isRunning = false;
   61	   }
   63	   private long elapsedTime;
   64	   private long startTime;
   65	   private boolean isRunning;
   66	}