How to subscribe to Flux/Mono in reactive programming? What options are available?

In reactive programming in Java using Project Reactor for subscribing to Flux or Mono, there are several options:

1. The subscribe() method — the basic way to subscribe and handle elements, errors, and completion:

flux.subscribe(
    value -> System.out.println("Received: " + value),
    error -> System.err.println("Error: " + error),
    () -> System.out.println("Completed")
);

2. Using Consumer to handle only values:

mono.subscribe(value -> System.out.println("Result: " + value));

3. Subscription with Disposable:

Disposable disposable = flux.subscribe();
// You can cancel the subscription later
disposable.dispose();

4. Subscription using doOnNext, doOnError, doOnComplete for side effects:

flux
  .doOnNext(value -> System.out.println("Received: " + value))
  .doOnError(error -> System.err.println("Error: " + error))
  .doOnComplete(() -> System.out.println("Completed"))
  .subscribe();

5. Subscription with a Subscriber:

You can implement the Subscriber interface for more fine-grained control over the subscription, such as managing backpressure.

flux.subscribe(new BaseSubscriber<>() {
    @Override
    protected void hookOnNext(T value) {
        System.out.println("Received: " + value);
        request(1); // Request the next element
    }
});

Thus, the choice of subscription method depends on your needs: simple processing, managing the subscription lifecycle, or controlling the data flow.