How to convert List> to Mono>?

Question

I have a method that returns Mono

:

interface Processor {
  Mono
 process(Input input);
}

And I want

Answer 1

If you don't have to create stream for any reason, you could create Flux from your inputs, map it and collect list

Flux.fromIterable(inputs).flatMap(processor::process).collectList();

Answer 2

// first merge all the `Mono`s:
List<Mono<Output>> outputs = ...
Flux<Output> merged = Flux.empty();
for (Mono<Output> out : outputs) {
    merged = merged.mergeWith(out);
}

// then collect them
return merged.collectList();

or (inspired by Alexander's answer)

Flux.fromIterable(outputs).flatMap(x -> x).collectList();