I was a little puzzled by this compared to what I was used to with Java in the past. It looks like the grandparent's code relies on JEP 445 ( https://openjdk.org/jeps/445 ) which is a preview feature as was mentioned but it also apparently requires the very latest Java 21 which hasn't even been officially released yet.
> And you still need a wrapper class with a static method main in it
One of the preview features he's using is JEP 445[1] that allows you to omit the wrapper class, as well as the arguments to main and the public and static modifiers.
Did not you still need the `java --source 11 ${filename_without_java_extension_because_JEP_330}` to use it? And you still need a wrapper class with a static method main in it.