使用ExecutorService时，线程安全内的类是否安全？

Question

I have an implementation of a Runnable class which contains a Vector of objects that items are removed from one by one and processed.

Using the ExecutorService and creating a newFixedThreadPool with n number of threads, are there n number of instances of the Runnable class? If so, are the classes and the Vector within threadsafe, or would this need to be implemented using synchronized?

Thanks

Answer 1

You are using newFixedThreadPool so it means, at any point max n threads are active. If you start n Runnables and all threads are busy, every additional Runnable will wait until a thread is available.

Your implementation has no shared resources (at least it looks like so) between runnables. In this case you don't need synchronization. But if, for example, you have one instance of vector and multiple instances of your 'workers', in that case you need synchronization.

Answer 2

As others have stated, if you are sharing your Vector across Runnables, then it is not threadsafe. To be threadsafe, you should use either bound queue (like BlockingQueue) or unbound queue (like ConcurrentLinkedQueue) instead of Vector.