Collections.synchronizedList and synchronized

Question

List<String> list = Collections.synchronizedList(new ArrayList<String>()); synchronized (list) {     list.add("message"); } 

Is the block "synchronized (list){} " really need here ?

Answer 1

You don't need to synchronize as you put in your example. HOWEVER, very important, you need to synchronize around the list when you iterate it (as noted in the Javadoc):

It is imperative that the user manually synchronize on the returned list when iterating over it:

List list = Collections.synchronizedList(new ArrayList()); ... synchronized(list) {     Iterator i = list.iterator(); // Must be in synchronized block     while (i.hasNext())         foo(i.next());    }