The document shows line graphs comparing the performance of Ruby versions and JRuby over time on benchmarks. It also provides code examples for using Java from JRuby, evaluating JRuby code from Java, and using the foreign function interface to call the C getlogin() function from JRuby.

4. 12.0 Ruby 1.8.7
Ruby 1.9.1
10.0 JRuby 1.4.0
8.0
6.0
4.0
2.0
0
100 200 300 400 500

6. camelCase() snail_case()
java_send java_alias

7. require 'java'
import javax.swing.JFrame
import javax.swing.JButton
frame = JFrame.new 'Hello Application'
button = JButton.new 'Hello World!'
button.add_action_listener do
frame.dispose
end
frame.get_content_pane.add button
frame.pack
frame.set_visible true

8. ScriptingContainer

9. ScriptEngineManager manager
= new ScriptEngineManager();
ScriptEngine engine
= manager.getEngineByName("jruby");
engine.eval("puts "Hello World!"");

10. require 'ffi'
module Kernel
extend FFI::Library
attach_function :getlogin,
[],
:pointer
end
puts getlogin.read_string