A parallel HttpClient sendAync question

Weijun Wang weijun.wang at oracle.com
Tue Nov 13 02:35:07 UTC 2018

I'm scanning a file and downloading links inside:

lines.flapMap(x -> Stream.ofNullable(findURIFrom(x)))
     .map(l -> download(c, l))
     .forEach(f -> f.join());

CompletableFuture<HttpResponse<Path>> download(HttpClient c, URI link) {
    return c.sendAsync(HttpRequest.newBuilder(link).build(),

However, it seems the download is one by one and not parallel. I guess maybe map() is lazy and each request is only send when forEach() is called and the next one is only sent after join().

I can only collect the jobs into a list and then call join() on CompletableFuture.allOf(list). Is there a simpler way?


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