code: public static <E extends PreferenceTypeAdapter<?, ?>> E getAdapter(Class<E> clazz) {
  		@SuppressWarnings("unchecked")
  		E adapter = (E) cache.get(clazz);
  
  		if (adapter == null) {
  			adapter = generateAdapter(clazz);
  		}
  
  		return adapter;
  	}
docs: Gets the adapter.
  
  @param <E> the element type
  @param clazz the clazz
  @return the adapter