CompletableFutureSequence.java

    public static <T> CompletableFuture<List<T>> sequence(final List<CompletableFuture<T>> futures) {
        return CompletableFuture.allOf(futures.toArray(new CompletableFuture[futures.size()]))
                .thenApply(unit -> futures
                        .stream()
                        .map(CompletableFuture::join)
                        .collect(toList()));
    }