Collection, and therefore also List, has a method called addAll to add all elements of any other collection in one go. For List, addAll will add all those elements at the end. So just create a new List, and call addAll for all Lists whose contents need to be added.
. . . and Lists retain insertion order as a default behaviour. You would have to look in the documentation for addAll to see which order it adds in. It says in the Java™ Tutorials that addAll concatenates Lists.