code: public List<TriggerListener> getInternalTriggerListeners() {
  
      synchronized (internalTriggerListeners) {
        return java.util.Collections.unmodifiableList(
            new LinkedList<TriggerListener>(internalTriggerListeners.values()));
      }
    }
docs: Get a list containing all of the <code>{@link org.quartz.listeners.TriggerListener}</code>s in
  the <code>Scheduler</code>'s <i>internal</i> list.