private synchronized void startUpdateThread(){
  if (screenUpdater == null) {
    screenUpdater=AccessController.doPrivileged((PrivilegedAction<Thread>)null);
    screenUpdater.start();
  }
 else {
    wakeUpUpdateThread();
  }
}

private synchronized void startUpdateThread ( ) { if ( screenUpdater == null ) { screenUpdater = AccessController . doPrivileged ( ( PrivilegedAction < Thread > ) null ) ; screenUpdater . start ( ) ; } else { wakeUpUpdateThread ( ) ; } }
if the update thread hasn ' t yet been created , it will be ; otherwise it is awaken
