JRuby 9.0.0.0 now available on Heroku
Change effective on 22 July 2015
The Ruby stack now supports JRuby 9.0.0.0. To use this release, add the following code to your Gemfile:
ruby '2.2.2', :engine => 'jruby', :engine_version => '9.0.0.0'
The JRuby 9.0.0.0 release notes can be found on the JRuby website.