Is it possible to get the first element from flux without converting flux into stream?

Question

score 24 · Accepted Answer · answered Mar 06 '19 at 14:05

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Alternatively to take(1), if you need a Mono<T> that represents the first element of the Flux<T> you can use .next().

Or if you need the i-th element, use .elementAt(i) (must be sure that such an element exists though, unlike take and next which just return an empty publisher if not enough elements).

answered Mar 06 '19 at 14:05

Simon Baslé

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Thanks @Simon for you reply. I idea here is to sort the Flux first and then get the first element. After seeing the docs I can achieve the same by using reduce on the flux as below. Flux.just(1, 2, 3) .reduce((o1, o2) -> { if (o1 - o2 < 0) { return o1; } return o2; }) – akreddy.21 Mar 07 '19 at 06:18

score 4 · Answer 2 · edited Mar 05 '19 at 17:22

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Flux.range(1,10).take(1) should do the trick (the range(...) part here is only to emit some sample values; if you blockFirst() or subscribe() to the stream, you should see '1')

edited Mar 05 '19 at 17:22

Mikhail Kholodkov

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answered Mar 05 '19 at 13:26

Frischling

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kerbermeister · Answer 3 · 2023-02-14T15:05:15.863

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Also the easiest: you can convert your Flux to Mono using Mono.from()

Mono<T> mono = Mono.from(flux);

It takes the first element of flux or completes with empty if flux has not emitted any element.

edited Feb 14 '23 at 15:05

answered Jan 31 '23 at 20:20

kerbermeister

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Is it possible to get the first element from flux without converting flux into stream?

3 Answers3