The Flow.Subscriber interface is used to receive messages, and its implementation is shown here:

public static interface Flow.Subscriber<T>

This interface is set up to receive messages. It only takes one argument—the subscribed item type, <T>. It has the following methods:

• void onComplete()
• void onError(Throwable throwable)
• void onNext(T item)
• void onSubscribe(Flow.Subscription subscription)