$ javac src/NullCase.java && java NullCase     (25.0.4.1+1-LTS)
without case null: NullPointerException
with case null: null!
case null, default: null or something else
instanceof with null: false

$ javac src/NullCase.java && java NullCase     (27+35)
without case null: NullPointerException
with case null: null!
case null, default: null or something else
instanceof with null: false

$ javac src/Unnamed.java && java Unnamed     (21.0.10+7-Ubuntu-124.04)
src/Unnamed.java:9: error: unnamed variables are a preview feature and are disabled by default.
            case Circle _ -> "round";          // the type matters, the value does not
                        ^
  (use --enable-preview to enable unnamed variables)
1 error

$ javac src/Unnamed.java && java Unnamed     (25.0.4.1+1-LTS)
round angular
5

$ javac src/Unnamed.java && java Unnamed     (27+35)
round angular
5