Is there a way to load classes of a certain package dynamically in android?

I need to load classes from a certain package dynamically.

What I don´t want to do is this:

 DexFile df = new DexFile(context.getPackageCodePath());
 for (Enumeration<String> it = df.entries(); it.hasMoreElements(); ) {
            String s = it.nextElement();
 }

As it is too slow if my app contains certain libraries as Google Play services, support lib and so on.

is there a way to load classes from a certain package inside the dexfile without filtering all classes first?