How can i convert an ArrayList to Flux?

I want to convert an ArrayList<Apple> to Flux<Apple>

To answer the question directly - you can use Flux.fromIterable(). Each element in the list will be an element in the flux.

...but I'd also advise caution and rethinking your reasons for doing this here. A flux deals with a reactive stream of elements that are processed individually, a collection is a group of elements all contained within memory at once. If you already have a collection in memory, then you're not really gaining anything by "pretending" it's a reactive stream. You can view it as the equivalent of Flux.just() for collections - often seen in demos, less so in real-world use.

Quick demonstrations aside, about the only valid reason for doing this is if you're using an API that requires a flux of elements, but the only thing you're able to obtain for whatever reason is a list.