java.lang.NullPointerException

[Dillinger4]

Arghhhhh. Can anyone see what i am doing wrong. The static format method takes a String and an Object[] as arguements. public static String format(String pattern, Object[] arguements) I have to create a Long object and put that into an Object array to pass to the format method but i keep getting a NullPointerException.
Any ideas why?

Sun should have just overloaded the format method to take various datatypes instead of an Object[] array.

class TimeTracker extends TimerTask{
   private Timer timer;
   private Long l;
   private TimeTrackerTest t;
   private long millis;
   Object[] o; 

  public TimeTracker(JTextField jtf){
   this.t = t;
   o = new Object[1];
   timer = new Timer(true); 
 }

 public void run(){
   try{
     millis = scheduledExecutionTime();
     l = new Long(millis); 
     o[0] = l; 
  
     t.jtf.setText(MessageFormat.format("{0}",o));
     }catch(Exception e){System.err.println(e);}
  }
}