There may be problems using the latest MRI ruby releases (should work OK with ruby-2.6), default setup is to use most recent JRuby, rather than a combination of MRI ruby and JRuby-Complete.
Many Rubyists use Ruby managers to manage multiple Rubies. They confer various advantages but are not officially supported. Their respective communities are very helpful, however do not use them unless you absolutely must, they are generally an absolute pain and not needed for JRubyArt (which ultimately runs directly from
java when using
jruby-complete or from an installed
jruby over which rvm and rbenv have no control over, you have been warned)
For windows see JRuby wiki
For Arch Linux
$ sudo pacman -S jruby
This should install the latest stable JRuby version.
For Debian linux
Get the latest version from http://jruby.org/download
cd /opt tar xzvf /pathToDownload/jruby-bin-9.3.x.x.tar.gz
You could the use the excellent update-alternatives to provide symbolic links to ruby, jruby, jirb jgem etc.
For MacOS user using the Homebrew as a package manager.
$ brew install jruby
This will again generally install the the latest jruby for you.
As far as I know rvm and rbenv are completely useless with jruby (further bundler is also as good as useless for JRubyArt)