Flux<String> fl = Flux.just("a", "b", "c");
Mono<String> mn = Mono.just("hello");
In many cases, you are doing some computation or calling a service and you expect exactly one result (or maybe zero or one result), and not a collection that contains possibly multiple results. In such cases, it's more convenient to have a
Compare it to "regular" Java: you would not use
List as the return type of any method that can return zero or one result. You would use
Optional instead, which makes it immediately clear that you do not expect more than one result.