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kotlinlang

Hello! Does `.forEach{it-&gt;}` guarantee the original sequence during execution?

Though not all collections preserve order

Thanks! This seems to be different from the `stream().forEach()` of `java`

<https://kotlinlang.slack.com/archives/C0B8MA7FA/p1646125840005099?thread_ts=1646125736.314299&amp;cid=C0B8MA7FA>
This refers to a collection that is itself unordered, right?:thinking_face:

&gt;  This seems to be different from the `stream().forEach()` of `java` 
I believe it’s not different except if you use parallel stream

It’s not different on practice, but order is not specified (and parallel stream is an example where forEach will not executed in the same order)_

So I would say that you should first be sure about what kind forEach you are talking about, Collection.forEach ( either Java and Kotlin extension) just use iterator order and order of forEach will be the same as order of this collection iterator implementation

It's actually exactly the same as for `stream().forEach()` in Java.
If the Stream is ordered and sequential, `forEach` will preserve the order. If the stream is unordered or parallel, order might not be preserved.

Same for `forEach` in Kotlin. If the collection you run it on preserves order, `forEach` preserves order too, if no, then not.

Parallel stream is still quite a different case

Ah, well, actually `forEach` does have no guarantee even for ordered sequential stream, but there the order usually is preserved.
Forgot about `forEachOrdered` which adds this guarantee for ordered streams, no matter whether sequential or parallel.