#fixed code
                                public void start()
    {
        if (State.NOT_STARTED.equals(this.state))
        {
            if (logger.isDebugEnabled())
                logger.debug("Transcriber is now transcribing");

            updateDDClient(DD_ASPECT_START);

            this.state = State.TRANSCRIBING;
            this.executorService = Executors.newSingleThreadExecutor();

            TranscriptEvent event
                = this.transcript.started(roomName, roomUrl, getParticipants());
            if (event != null)
            {
                fireTranscribeEvent(event);
            }
        }
        else
        {
            logger.warn("Trying to start Transcriber while it is" +
                            "already started");
        }
    }
#vulnerable code 
                                public void start()
    {
        if (State.NOT_STARTED.equals(this.state))
        {
            if (logger.isDebugEnabled())
                logger.debug("Transcriber is now transcribing");

            StatsDClient dClient = JigasiBundleActivator.getDataDogClient();
            if(dClient != null)
            {
                dClient.increment(DD_ASPECT_START);
                if(logger.isDebugEnabled())
                {
                    logger.debug("thrown stat: " + DD_ASPECT_START);
                }
            }

            this.state = State.TRANSCRIBING;
            this.executorService = Executors.newSingleThreadExecutor();

            List<Participant> participantsClone;
            synchronized (this.participants)
            {
                participantsClone = new ArrayList<>(this.participants.size());
                participantsClone.addAll(this.participants.values());
            }

            TranscriptEvent event
                = this.transcript.started(roomName, roomUrl, participantsClone);
            if (event != null)
            {
                fireTranscribeEvent(event);
            }
        }
        else
        {
            logger.warn("Trying to start Transcriber while it is" +
                            "already started");
        }
    } 
                            #location 19 
                            #vulnerability type THREAD_SAFETY_VIOLATION