DB db = mongo.getDB("yourDbName");
DBCollection coll = db.getCollection("person");

DBObject query = new BasicDBObject();
query.put("dateCreated", new BasicDBObject($exists : true));

DBCursor cur = coll.find(query).sort(new BasicDBObject("dateCreated", 1)).limit(10);
while(cur.hasNext()) {
    DBObject obj = cur.next();
    // Get data from the result object here
}