Question

Documentation on synchronizedList states that,

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());
}

Failure to follow this advice may result in non-deterministic behavior.

This seems pretty clear, but I just wanted to confirm that a for each loop is prohibited. For example, I cannot do something like as follows right?

List<MyType> list = Collections.synchronizedList(new ArrayList(<MyType>));
...
synchronized(list){
    for(MyType m : list){
        foo(m);
        m.doSomething();
    }
}

Answer 1

Yes, you can – your enhanced for loop is basically the same as your code which explicitly uses the iterator. It boils down to the same code – it’s just calling iterator() and then alternating between next() and hasNext() calls.