output: #fixed code
                                  @Override
      public void start(ExtendedSequenceNumber extendedSequenceNumber, InitialPositionInStreamExtended initialPositionInStreamExtended) {
          if (executorService.isShutdown()) {
              throw new IllegalStateException("ExecutorService has been shutdown.");
          }
  
          publisherSession.init(extendedSequenceNumber, initialPositionInStreamExtended);
  
          if (!started) {
              log.info("{} : Starting prefetching thread.", shardId);
              executorService.execute(defaultGetRecordsCacheDaemon);
          }
          started = true;
      }
input: #vulnerable code 
                                  @Override
      public void start(ExtendedSequenceNumber extendedSequenceNumber, InitialPositionInStreamExtended initialPositionInStreamExtended) {
          if (executorService.isShutdown()) {
              throw new IllegalStateException("ExecutorService has been shutdown.");
          }
  
          this.initialPositionInStreamExtended = initialPositionInStreamExtended;
          highestSequenceNumber = extendedSequenceNumber.sequenceNumber();
          dataFetcher.initialize(extendedSequenceNumber, initialPositionInStreamExtended);
  
          if (!started) {
              log.info("{} : Starting prefetching thread.", shardId);
              executorService.execute(defaultGetRecordsCacheDaemon);
          }
          started = true;
      } 
                              #location 8 
                              #vulnerability type THREAD_SAFETY_VIOLATION