Java 8 - Map an Array/Collection in place

Question

Is there a way in Java 8 to transform an Array/Collection using map() without having to reassign the created copy, e.g.

Arrays.stream(array).mapInPlace(x -> x / 100);
list.stream().mapInPlace(e -> e.replaceAll(" ", ""));

instead of

array = Arrays.stream(array).map(x -> x / 100).toArray();
list = list.stream().map(e -> e.replaceAll(" ", "")).collect(Collectors.toList());

?

If not, what's the reason for this design decision?

Youcef LAIDANI · Accepted Answer · 2018-09-05 10:55:49Z

9

Maybe using List::replaceAll in your case can help you :

Arrays.asList(array).replaceAll(x -> x / 100);

and

list.replaceAll(e -> e.replaceAll(" ", ""));

Good point from @Holger, in case you need the index you can use Arrays::setAll :

Arrays.setAll(array, x -> array[x] / 100);

Or more better if you want your job to be in parallel you can use Arrays::parallelSetAll :

Arrays.parallelSetAll(array, x -> array[x] / 100);

answered Sep 5, 2018 at 10:20

Youcef LAIDANI

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2 Comments

…and in case you need the index, Arrays.setAll(array, index -> expression);

Thank you @Holger this is nice trick even we can use parallelSetAll