package com.test;

public class Main {

    public static void main(String[] args) {
        DatabaseService databaseService = new DatabaseService();
        MongoDB mongoDB = new MongoDB();
        OracleDB oracleDB = new OracleDB();

        // Both can commit
        databaseService.commit(oracleDB);
        databaseService.commit(mongoDB);

        // Only Oracle can commit, Mongo will not pass
        databaseService.makeTransaction(oracleDB);
        databaseService.makeTransaction(mongoDB); // Compiler error because of incompatible types
    }
}

interface Database {

    void commit();
}

interface TransactionalDatabase extends Database {

    void openTransaction();
}

class DatabaseService {

    public void commit(Database database) {
        database.commit();
    }

    public void makeTransaction(TransactionalDatabase database) {
        database.openTransaction();
        database.commit();
    }
}

class OracleDB implements TransactionalDatabase {

    @Override
    public void commit() {
        System.out.println("OracleDB commit");
    }

    @Override
    public void openTransaction() {
        System.out.println("OracleDB opens transaction");
    }
}

class MongoDB implements Database {

    // No transactions at all

    @Override
    public void commit() {
        System.out.println("Mongo commit");
    }
}