Ian

public class LargeSerializableConcurrentSkipListMap<K, V> extends
        ConcurrentSkipListMap<K, V> {
    private static final long serialVersionUID = -1525292268623732635L;

    private void writeObject(ObjectOutputStream stream) throws IOException {
        for (Map.Entry<K, V> e : this.entrySet()) {
            stream.writeObject(e.getKey());
            stream.writeObject(e.getValue());
        }
        // We do it like this because items can be added and removed
        // during serialization and an "end of object" indicator is more
        // robust given this
        stream.writeObject(new EndObject());
        stream.writeObject(new EndObject());
    }

    @SuppressWarnings("unchecked")
    private void readObject(ObjectInputStream stream) throws IOException,
            ClassNotFoundException {
        while (true) {
            Object k = stream.readObject();
            Object v = stream.readObject();
            if ((k instanceof EndObject) && (v instanceof EndObject)) {
                break;
            }
            this.put((K) k, (V) v);
        }
    }

    private static class EndObject implements Serializable {
        private static final long serialVersionUID = -5347717251973679220L;
    }
}