private static class PersistentQueueSerializer extends CollSerializer<PersistentQueue> {
@Override
public PersistentQueue read(Kryo kryo, Input input, Class<PersistentQueue> type) {
final int size = input.readInt();
PersistentQueue q = PersistentQueue.EMPTY;
for (int i = 0; i < size; i++)
q.cons(kryo.readClassAndObject(input));
return q;
}