On page 80 (at the bottom) you execute the command

(first (System/getProperties))

and on top of page 81 you show the output as

` → #object[java.util.Hashtable$Entry 0x12468a38
“java.runtime.name=Java™ SE Runtime Environment”]

However, If I execute this command, I receive

>java --version
openjdk 21.0.2 2024-01-16
OpenJDK Runtime Environment (build 21.0.2+13-58)
OpenJDK 64-Bit Server VM (build 21.0.2+13-58, mixed mode, sharing)

>clj --version
Clojure CLI version (deps.clj) 1.12.4.1582

>clj
Clojure 1.12.4
user=> (first (System/getProperties))
#object[java.util.concurrent.ConcurrentHashMap$MapEntry 0x1e7f2e0f “java.specification.version=21”]

i.e. the type is a ConcurrentHashMap-Entry, although Properties is still an extension of the very old class Hashtable. Seems to be a Clojure effect.

I propose to just change the printed output.