code: public static <T> ConjunctFuture<Collection<T>> combineAll(Collection<? extends CompletableFuture<? extends T>> futures) {
  		checkNotNull(futures, "futures");
  
  		return new ResultConjunctFuture<>(futures);
  	}
docs: Creates a future that is complete once multiple other futures completed.
  The future fails (completes exceptionally) once one of the futures in the
  conjunction fails. Upon successful completion, the future returns the
  collection of the futures' results.
  
  <p>The ConjunctFuture gives access to how many Futures in the conjunction have already
  completed successfully, via {@link ConjunctFuture#getNumFuturesCompleted()}.
  
  @param futures The futures that make up the conjunction. No null entries are allowed.
  @return The ConjunctFuture that completes once all given futures are complete (or one fails).