Reflection - Method caching for multiple subclasses

I've got one abstract class which is extended by multiple concrete classes. The abstract class initialization block fetch all the methods of the current class hierarchy searching for particular annotated methods.

ConcreteClass2 > ConcreteClass1 > AbstractClass
OtherConcrete1 > AbstractClass

---

{
   ...

   final List<Method> methods = new ArrayList<>(16);
   Clazz<?> clazz = getClass();

   while (clazz != Object.class) {
      for (final Method method : clazz.getDeclaredMethods()) {
         if (method.isAnnotationPresent(MyAnnotation.class)) {
            methods.add(method);
         }
      }

      clazz = clazz.getSuperclass();
   }

   METHODS.put(getClass(), methods);

   ...
}

These concrete classes are instantiated in a web/application server and are used inside Servlets.

As per se Reflection is not the fastest, and as I do not want to repeat the scan every time a concrete type is instantiated (new), what is the best strategy to cache the annotated Method's.

I'm actually using ConcurrentHashMap as <Class<? extends AbstractClass>, List<Method>>, and In the initialization block I check if the Map already contains an entry for the uppermost concrete type.

However I do not think this is the best way to handle it. And by the way, I cannot have external dependencies.