public void addTimeBoundsListener(TimeBoundsListener tbl){
  if (!timeBoundsListeners.contains(tbl)) {
    timeBoundsListeners.add(tbl);
  }
}

public void addTimeBoundsListener ( TimeBoundsListener tbl ) { if ( ! timeBoundsListeners . contains ( tbl ) ) { timeBoundsListeners . add ( tbl ) ; } }
add a timeboundslistener to the clock , so it knows who to tell when the time bounds change .
