in groupJoin method,the param 'TrightEnd' is type UnicastProcessor but size = 0

public static void testGroupJoin(){
    Flux<Integer> f1 = Flux.just(1,2,3,10,11,12,13,14);
    Flux<Integer> f2 = Flux.just(10,12,13,14,15,16);
    f1.groupJoin(f2,x->Flux.never(),y-> Flux.never(),(x,y)->{
        return x+","+y;
    }).subscribe(System.out::println);
}

the y.size = 0 i dont know why;

i try use method join() , is running well;

public static void testJoin(){
    Flux<Integer> f1 = Flux.just(1,2,3,10,11,12,13,14);
    Flux<Integer> f2 = Flux.just(10,12,13,14,15,16);
    f1.join(f2,x->Flux.never(),y-> Flux.never(),(x,y)->{
        return x+","+y;
    }).subscribe(System.out::println);
}

i want get data {1:(10,12,13,14,15,16)},{2:(10,12,13,14,15,16)}.... and i know achieve the effect by use method join() and groupBy() i just want know groupJ开发者_如何学运维oin how to work