Talk by Charles Nutter, on Friday 2nd March

How to install JRuby :

• rvm  install jruby and unzip or
• download tar/zip file from jruby.org or
• you can use a windows installer from jruby.org

What is bad compared to pure Ruby ?

• memory footprint, mostly due to the (better) GC; objects are larger, but fewer; BUT : lower memory when using concurrency (for example using rails, each http request will spawn a new Ruby process consuming the same amount of RAM, compared to JRuby  spawning some new threads and keeping its amount of RAM consumed stable and keeping barriers between those threads)
• c extensions, still experimental

Good

• Ruby itself (both 1.8.7 and 1.9.2. modes in the same jruby : start it with jruby –1.9)
• sandboxed jruby (for non thread safe programs, runs in isolated mode)

JVM

• best GC, support dynamic language
• ruby code used with Jruby ends up in native code, optimized by the JVM
• stable threading : jvm threads are OS threads;
• libraries : tens of thousands of JVM library(Swing demo : Charles built a Swing panel with a button adding statements to jirb )
• lots of tools : visualvm (demo stressed gc with old and young objects)
• invoke dynamic : ruby is about calling methods, the jvm from 1.7 optimizes those calls

Android

• Ruboto : gem install ruboto ; ruboto app; rake : you’re done creating an Android app with JRuby
• Ruboto irb
• Jruby 1.7 : invoke dynamic, dalvik enhancement, ruby 1.9 by default

Bonus

• Charles used the redcar editor, written in jruby + swt
• trinidad : tomcat like launcher with ruby wrapper
• torquebox : jboss like launcher (messaging, schedulers, etc…)
• During his Android demo, Charles used android screencast
• warbler for war/jar : to wrap your ruby app in a war
• you can deploy your apps to engine yard cloud