code: public synchronized void transitionEvent(boolean isEmpty)
    {
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.entry(tc, "transitionEvent", new Object[]{ new Boolean(isEmpty)});
  
      if(isEmpty)
      {
        transition--;
      }
      else
      {
        transition++;
      }
  
      if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
        SibTr.exit(tc, "transitionEvent", new Integer(transition));
    }
docs: Method transitionEvent
  
  Called when the number of consumers for a registered callback drops to zero
  or rises above zero.
  
  @param toEmpty