JavaScript cannot attach file to email

Add-ons Bindings
10

I wonder if this part is wrong as well as I cannot get it to work.

import java.util.List

val List<String> attachmentUrlList = newArrayList(
  "http://some.web/site/snap.jpg&param=value",
  "file:///tmp/201601011031.jpg")

I am now able to send a single attachment but not multiple…yet.