@SuppressWarnings("unchecked")
  public static <T> List<T> getExtensionList(Class<T> clazz, boolean isSingleton) {
    if (isSingleton) {
      List<T> extensions = (List<T>) SINGLETON_OBJECTS.get(clazz);
      if (extensions != null && !extensions.isEmpty()) {
        return extensions;
      }
    }

    synchronized (getLoadClassLock(clazz)) {
      if (!isSingleton) {
        return load(clazz);
      }

      if (SINGLETON_OBJECTS.containsKey(clazz)) {
        return (List<T>) SINGLETON_OBJECTS.get(clazz);
      }

      List<T> serviceList = load(clazz);
      if (serviceList != null && !serviceList.isEmpty()) {
        SINGLETON_OBJECTS.put(clazz, serviceList);
      }
      return serviceList;
    }
  }
Get extension class list order by {@link Order}
src/main/java/com/eudemon/ratelimiter/extension/ExtensionLoader.java