How to parallely iterate a collection in java?

Question

Is it possible to iterate a Collection parallel in Java. I'm looking for something like c# Parallel.ForEach in System.Threading.Tasks-Namespace

Java8: `collection.stream().parallel().forEach(...)` – Konstantin Yovkov Oct 28 '15 at 11:51 — Konstantin Yovkov, Oct 28 '15 at 11:51

score 2 · Answer 1 · edited May 23 '17 at 11:44

2

The Stream API in Java 1.8 was designed with parallelism in mind, so you can convert any Stream to a parallel stream. for example:

 Stream.of(1,2,3,4,5,6,7).parallel().forEach(System.out::println);

And In fact every Stream can be converted into a parallel one

Stream<Integer> parallel = stream.parallel();

And Collection provides a method that return a parallelStream.

Stream<Integer> parallel = Arrays.asList(1,2,3).parallelStream();

Now, this does not mean every operation can be efficiently parallelised, it depends on the nature of the source collection and the task you doing. Check this out

edited May 23 '17 at 11:44

Community

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answered Oct 28 '15 at 11:54

Sleiman Jneidi

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Indeed. Be very careful about using `parallel()`, it has a lot of caveats and shouldn't be used without fully understanding what it does. – Kayaman Oct 28 '15 at 12:00
@Sleiman: I'm using Java 1.7 Any other way to achieve it in Java 1.7 – Vinoth Sankar Oct 28 '15 at 12:29
@VinothSankar probably RxJava is the best, but your code wouldn't be concise – Sleiman Jneidi Oct 28 '15 at 12:33

score 1 · Answer 2 · answered Oct 28 '15 at 11:53

1

Assuming you're on Java 8, you should use streams. If you're not on Java 8, there's no baked-in equivalent.

sandwichCollection.parallelStream().forEach((sandwich) -> {
    sandwich.eat();
});

answered Oct 28 '15 at 11:53

wadda_wadda

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How to parallely iterate a collection in java?

2 Answers2