#fixed code
                                @Override
    public ListenableFuture<IBigQueue> queueReadyForDequeue() {
        initializeFutureIfNecessary();
        return dequeueFuture;

    }
#vulnerable code 
                                @Override
    public ListenableFuture<IBigQueue> queueReadyForDequeue() {
        futureLock.lock();
        if (dequeueFuture == null || dequeueFuture.isDone() || dequeueFuture.isCancelled()) {
            dequeueFuture = SettableFuture.create();
        }
        futureLock.unlock();
        return dequeueFuture;

    } 
                            #location 8 
                            #vulnerability type THREAD_SAFETY_VIOLATION