Choosing the best concurrency list in Java

Any Java collection can be made to be Thread-safe like so:

List newList = Collections.synchronizedList(oldList);

Or to create a brand new thread-safe list:

List newList = Collections.synchronizedList(new ArrayList());

http://download.oracle.com/javase/6/docs/api/java/util/Collections.html#synchronizedList(java.util.List)

ConcurrentLinkedQueue uses a lock-free queue (based off the newer CAS instruction).

had better be List

The only List implementation in java.util.concurrent is CopyOnWriteArrayList. There's also the option of a synchronized list as Travis Webb mentions.

That said, are you sure you need it to be a List? There are a lot more options for concurrent Queues and Maps (and you can make Sets from Maps), and those structures tend to make the most sense for many of the types of things you want to do with a shared data structure.

For queues, you have a huge number of options and which is most appropriate depends on how you need to use it:

• ConcurrentLinkedQueue
• ArrayBlockingQueue
• LinkedBlockingDeque
• LinkedBlockingQueue
• PriorityBlockingQueue
• SynchronousQueue
• DelayQueue

If the size of the list if fixed, then you can use an AtomicReferenceArray. This would allow you to perform indexed updates to a slot. You could write a List view if needed.