How many elements can Flux accept in Project Reactor?

Flux in Project Reactor can accept any number of elements — from zero to infinity. Flux represents a stream of 0..N elements, unlike Mono, which represents 0..1 element.

This allows using Flux for processing sequences of data of arbitrary length, for example:

Flux.just(1, 2, 3, 4, 5)
    .subscribe(System.out::println);

Thus, Flux is not limited in the number of elements and can be used for reactive processing of large or infinite data streams.