JRuby version 9.4.2.0 is now available

Change effective on 25 July 2023

JRuby v9.4.2.0 is now available on Heroku. To run your app using this version of Ruby, add the following ruby directive to your Gemfile:

ruby "3.1.0", engine: "jruby", engine_version: "9.4.2.0"

The JRuby release notes can be found on the JRuby website.