In "Creating Unmodifiable Lists, Sets, and Maps":

https://docs.oracle.com/en/java/javase/15/core/creating-immutable-lists-sets-and-maps.html

A collection is considered unmodifiable if elements cannot be added, removed, or replaced. After you create an unmodifiable instance of a collection, it holds the same data as long as a reference to it exists.

Should "data" be changed to "elements"?