https://www.java2s.com/example/java-utility-method/sortedset-create-index-0.html
Java Utililty Methods SortedSet Create
javamethodssortedsetcreate
https://www.cs.longwood.edu/java/docs/api/java/util/SortedSet.html
SortedSet (Java Platform SE 7 )
java platformsortedset
https://www.scala-lang.org/api/3.x/scala/collection/immutable/SortedSet.html
SortedSet
sortedset