% jshell
| Welcome to JShell -- Version 25
| For an introduction type: /help intro

jshell> \u0070\u0075\u0062\u006c\u0069\u0063 class MyClass { }
   ...>
| Error:
| repeated modifier
| \u0070\u0075\u0062\u006c\u0069\u0063 class MyClass { }
| ^

But,

jshell> public class MyClass {}
| created class MyClass

Looks like javac-like upfront \uXXXX is not done by jshell before making its own preprocessing (like completing/modifying snippet).