Sleep inside closure - Java 8 lambdas

Question

I know that this question sounds silly - I think that lambdas are execute in parallel, so when I run something like

List<Integer> list = ArrayList<Integer>();
list.add(3);
list.add(2);
list.add(1);
list.forEach(n -> System.out.println(""+n));

I woud not get "3\n2\n1\n" every time. I tried to make some kind of sleep() inside the closure, but it looks like that sleep the thread above, not each lambda execution. (Something like n -> { sleep(n*1000); System.out.println(""+n)}) Can this be done anyhow? Or am I wrong because some parallel stream, etc., should be used instead ordinaly not concurent list? Or is my idea totaly wrong?

Answer 1

forEach applied to an Iterable is generally executed sequentially. If you want parallel execution you need to create a parallel stream: list.parallelStream().forEach(...).