How to convert Stream to Stream

Question

Is there a way convert Stream<int[]> to Stream<Integer>

int[] arr2 = new int[] { 54, 432, 53, 21, 43 };
// Below gives me Stream<int[]> 

Stream.of(arr2);  // I want to convert it to Stream<Integer>

Related/Possible duplicate of [How do I convert a Java 8 IntStream to a List?](https://stackoverflow.com/questions/23674624/how-do-i-convert-a-java-8-intstream-to-a-list) and/or [How to convert int array to Integer array in Java?](https://stackoverflow.com/questions/880581/how-to-convert-int-to-integer-in-java) — Naman, Jan 11 '19 at 00:41

score 5 · Answer 1 · edited Jun 20 '20 at 09:12

5

You can use either Arrays.stream()

Arrays.stream(arr2).boxed();  // will return Stream<Integer>

Or IntStream.of

IntStream.of(arr2).boxed();   // will return Stream<Integer>

Stream<Integer> boxed()

Returns a Stream consisting of the elements of this stream, each boxed to an Integer.

This is an intermediate operation.

edited Jun 20 '20 at 09:12

Community

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answered Jan 11 '19 at 00:04

Ryuzaki L

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score 4 · Answer 2 · answered Jan 10 '19 at 23:54

4

box the stream:

Arrays.stream(arr2).boxed();

answered Jan 10 '19 at 23:54

Ousmane D.

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@AshishkumarSingh If you **really** insisted on starting with `Stream.of(arr2)` then you could do `Stream.of(arr2).flatMap(arr -> Arrays.stream(arr).boxed())`. But I don't know why you'd want to. – Michael Jan 11 '19 at 00:03
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@Michael or `Stream.of(arr2).flatMapToInt(Arrays::stream).boxed()` – Holger Jan 11 '19 at 09:41
@Holger I was looking for what you commented. I know it doesn't make much sense to use when we have `Arrays.stream(arr2).boxed()`, but I just wanted to learn how can I achieve it if we have `Stream` – Ashishkumar Singh Jan 11 '19 at 16:05

Gauravsa · Answer 3 · 2019-01-11T00:02:07.070

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You can use this:

Integer[] arr = Arrays.stream(arr2).boxed().toArray(Integer[]::new);

edited Jan 11 '19 at 00:02

answered Jan 10 '19 at 23:58

Gauravsa

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There is no method `boxed` for `arr2` – Ashishkumar Singh Jan 11 '19 at 00:00

jker · Answer 4 · 2019-01-11T19:07:45.307

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You can create Stream from io.vavr with

Stream.ofAll(arr2)

but you want to use stream of integers you should use IntStream. You can create IntStream from array like this:

Arrays.stream(arr2)

edited Jan 11 '19 at 19:07

answered Jan 11 '19 at 00:00

jker

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Oh i've used Stream class from io.vavr – jker Jan 11 '19 at 19:06

score 1 · Answer 5 · edited Apr 05 '21 at 16:21

There is an issue in this case.

Let's look at an example. If you have an array of primitives and try to create a stream directly you will have a stream of one array object, like this:

// Arrays of primitives 
int[] nums = {1, 2, 3, 4, 5}; 
Stream.of(nums); // One element int[] | Stream<int[]>

To solve this you can use:

Arrays.stream(nums).count();  // Five Elements 
IntStream.of(nums).count(); // Five Elements

How to convert Stream to Stream

5 Answers5