Java 7: missing CollectionsEmptySortedSetSerializer for Collections.emptySortedSet()

[reda-alaoui]

In Java 7, Collections.emptySortedSet() deserialization fails. It would be nice to add its serializer once this project hits Java 7:

class CollectionsEmptySortedSetSerializer extends Serializer<SortedSet<?>> {

        @Override
        public void write(Kryo kryo, Output output, SortedSet<?> object) {

        }

        @Override
        public SortedSet<?> read(Kryo kryo, Input input, Class<SortedSet<?>> type) {
            return Collections.emptySortedSet();
        }
    }