question: public String checkKeyAndGetDatabaseName ( String db ) { if ( key == null ) { return db ; } if ( key . equals ( db ) ) { return keyDatabase ; } throw DbException . get ( ErrorCode . WRONG_USER_OR_PASSWORD ) ; }
target:  If no key is set, return the original database name. If a key is set, check if the key matches. If yes, return the correct database name. If not, throw an exception.