import com.db4o.Db4o;
import com.db4o.ObjectContainer;
import com.db4o.ObjectSet;
import com.db4o.query.Query;
...

public class DbUtil {

  /**
  * save someObject to DB
  */
  public static void saveData(SomeClass someObject, String DbFilename) {
    ObjectContainer db=Db4o.openFile(DbFilename);
    try {
      db.set(idGenerator);
    }
    finally {
      db.close();
    }
  } //saveData(SomeClass ..)

  ..

} //DbUtil