Why should I use concurrent characteristic in parallel stream with collect?

Question

Why should I use concurrent characteristic in parallel stream with collect:

List list =
        Collections.synchronizedList(new ArrayList<         


        

Answer 1

Because of this : "Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a ConcurrentMap as a key or value happen-before actions subsequent to the access or removal of that object from the ConcurrentMap in another thread."