@Override public <C extends Collection<T>>CompletableFuture<C> toCollection(final Supplier<C> collectionFactory){
  return CompletableFuture.supplyAsync(null,exec);
}

@ Override public < C extends Collection < T > > CompletableFuture < C > toCollection ( final Supplier < C > collectionFactory ) { return CompletableFuture . supplyAsync ( null , exec ) ; }
asynchronously perform a stream collection
