How to fetch the index number while doing a flatMap() on a Flux

Question

I have a code block as below

var x = Flux.just("A", "B", "C", "D");
        x.flatMap(y -> {
            System.out.println(y);
            return Mono.just(y);
        }).subscribe();

This successfully prints:

A
B
C
D

Is there a way I can print the index/record number as well in addition to the String value?

A - 1
B - 2
C - 3
D - 4

Answer 1

You can try index():

x.index()
 .flatMap(y -> {
     System.out.println(y.getT2() + "-" + y.getT1());
     return Mono.just(y);
 })
 .subscribe();