#vulnerable code 
                                @Override
    public void close() {
        if (graphDatabaseService != null) {
            graphDatabaseService.shutdown();
        }
    } 
                            #location 4 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public void close() {
        if (graphDatabaseService != null) {
            logger.debug(" *** Now shutting down embedded database instance: " + this);
            graphDatabaseService.shutdown();
            //
            graphDatabaseService = null;
        }
    }