IntervalMessageProducer.java

public abstract class IntervalMessageProducer {

    public static Flux<String> produce(int c) {
        return produce().take(c);
    }

    public static Flux<String> produce() {
        return doProduceCountAndStrings().map(CountAndString::message);
    }

    private static Flux<CountAndString> doProduceCountAndStrings() {
        var counter = new AtomicLong();
        return Flux //
                .interval(Duration.ofSeconds(1)) // <1>
                .map(i -> new CountAndString(counter.incrementAndGet())); //
    }

}

record CountAndString(String message, long count) {

    CountAndString(long count) {
        this("# " + count, count);
    }
}