private void checkShutdownHooks() {
    IdentityHashMap<Thread, Thread> checkedHooks = new IdentityHashMap<Thread, Thread>(getShutdownHooks());
    for (Thread t : markedHooks.values()) {
      checkedHooks.remove(t);
    }
    for (Thread t : checkedHooks.values()) {
      removeHook(t);
    }
  }
private void checkShutdownHooks()