In an earlier post I wrote about installing JRuby via RVM. In a footnote, I mentioned

JRuby 1.6.0, which should be out Any Day Now, is supposed to be fully compatible with Ruby 1.9.2.

Well, kids, that day is today. ¹

First update RVM to version 1.2.9 or higher.

  $ rvm get head
  $ rvm reload

Then install JRuby 1.6.0.

  $ rvm install jruby

RVM won’t remove any older version of JRuby you may have installed, so you have both available to do comparisons if you like. At the very least, you probably should copy over the installed gems so your JRuby 1.6.0 environment will behave as much like your older environment as possible.

  $ rvm gemset copy jruby-1.5.6 jruby-1.6.0

Now, let’s check it out.

  $ rvm use jruby-1.6.0
  Using /Users/craigc/.rvm/gems/jruby-1.6.0
  $ ruby -v
  jruby 1.6.0 (ruby 1.8.7 patchlevel 330) (2011-03-15 f3b6154) ¬
  (Java HotSpot(TM) 64-Bit Server VM 1.6.0_24) [darwin-x86_64-java]

Interesting – JRuby 1.6.0 is still supporting Ruby 1.8.7 out of the box. Enabling 1.9 support is the same as before.

  $ export JRUBY_OPTS="--1.9"
  $ ruby -v
  jruby 1.6.0 (ruby 1.9.2 patchlevel 136) (2011-03-15 f3b6154) ¬
  (Java HotSpot(TM) 64-Bit Server VM 1.6.0_24) [darwin-x86_64-java]

Once you’re confident the new JRuby is working correctly, it’s easy to remove the old one.

  $ rvm remove jruby-1.5.6