В чем отличие HTTP-прокси, туннеля, шлюза? [закрыто]

, как писал Алекс, но этот код подходит для версий 3.x

import com.mongodb.*;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;

public class TestAutoIncrement {

     private final static String DB_NAME = "MyTestDB";
     private final static String TEST_COLLECTION = "testCollection";
     private final static String COUNTERS_COLLECTION = "countersCollection";

     private static MongoCollection<Document> testCollection;
     private static MongoCollection<Document> countersCollection;

public static void main(String[] args) {

    MongoClient mongoClient = new MongoClient();
    MongoDatabase database = mongoClient.getDatabase(DB_NAME);
    testCollection = database.getCollection(TEST_COLLECTION);
    countersCollection = database.getCollection(COUNTERS_COLLECTION);

    if (countersCollection.count() == 0) {
        createCountersCollection();
    }

    createTestCollection();
    mongoClient.close();
}

public static void createCountersCollection() {

    Document document = new Document();
    document.append("_id", "userid");
    document.append("seq", 1);
    countersCollection.insertOne(document);
}

public static Object getNextSequence(String name) {

    Document searchQuery = new Document("_id", name);
    Document increase = new Document("seq", 1);
    Document updateQuery = new Document("$inc", increase);
    Document result = countersCollection.findOneAndUpdate(searchQuery, updateQuery);

    return result.get("seq");
}

public static void createTestCollection() {

    Document document = new Document();
    document.append("_id", getNextSequence("userid"));
    document.append("name", "Dinah");
    testCollection.insertOne(document);

    document = new Document();
    document.append("_id", getNextSequence("userid"));
    document.append("name", "Jonny");
    testCollection.insertOne(document);

    document = new Document();
    document.append("_id", getNextSequence("userid"));
    document.append("name", "Brody");
    testCollection.insertOne(document);
}

}