This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 11.28, “How to Use Sortable Sets in Scala”
You want to be able to store and retrieve items from a set in a sorted order.
To retrieve values from a set in sorted order, use a
SortedSet. To retrieve elements from a set in the order in which elements were inserted, use a
SortedSet returns elements in a sorted order: