Polyglot CheatSheet - None/Null/Nil
Null: a Trait.
null: an instance of Null
Nil: an empty List of anything of zero length. It refers to List which has no contents(not "refers to nothing")
Nothing: a Trait; a subtype of everything; not superclass of anything; no instances of Nothing.
None: a sensible return value to avoid null pointer exception. One of 2 subclasses of
Option, the other is
Unit– Type of method that doesn’t return a value of any sort.