PuneRb - JRuby talk - Saturday, October 7th, 2017

curve_swing.rb

require 'java'

java_import 'javax.swing.JFrame'
java_import 'javax.swing.JPanel'
java_import 'java.awt.Dimension'

class MyPanel < JPanel
  def paintComponent(graphics)
    1000.times do |i|
      x = Math.sin(i) + 1
      y = Math.cos(i * 0.2) + 1
      graphics.draw_oval(x * 320, y * 240, 10, 10)
    end
  end
end

frame = JFrame.new 'Hello, JRuby!'
frame.size = Dimension.new 640, 480
panel = MyPanel.new
frame.add panel
frame.visible = true

hello_world_swing.rb

require "java"

java_import javax.swing.JFrame
java_import javax.swing.JButton
java_import javax.swing.JOptionPane

class HelloWorld < JFrame
  def initialize
    super "Example"

    setSize(150, 100)
    setDefaultCloseOperation(JFrame::EXIT_ON_CLOSE)
    setLocationRelativeTo(nil)

    button = JButton.new("Say Hello")
    add(button)

    button.addActionListener do |e|
      JOptionPane.showMessageDialog(nil, "Hello World")
    end

    setVisible(true)
  end
end

HelloWorld.new

JRuby.md

swing_one_liner.rb

javax.swing.JOptionPane.showMessageDialog(nil, "Hello World!")

Talk links

warlber gem - https://rubygems.org/gems/warbler/
warbler github - https://github.com/jruby/warbler
warble commands
 - warble compiled    # Feature: precompile all Ruby files
 - warble executable  # Feature: make an executable archive (runnable..)
puma - http://puma.io (A modern, concurrent web server for Ruby, supports MRI and JRuby)

thread_cpu_bound.rb

require 'benchmark'

def task
  tmp_array = []
  10_000_000.times { |n| tmp_array << n }
end

task_method = method(:task)

@threads = []
Benchmark.bm(14) do |x| 

  x.report('no-threads') do
    2.times do
      task
    end
  end

  x.report('with-threads') do
    2.times do
      @threads << Thread.new(&task_method)
    end
    @threads.each(&:join)
  end
end

thread_io_bound.rb

require 'open-uri'
require 'benchmark'

URL = 'http://google.com'
TIMES = 15.times

puts "RUBY_PLATFORM #{RUBY_PLATFORM}"
puts "RUBY_VERSION #{RUBY_VERSION}\n\n"

def without_threads
  TIMES.map { open(URL) }
end

def with_threads
  TIMES.map do
    Thread.new { open(URL) }
  end.each(&:join)
end

Benchmark.bm do |x|
  x.report("Without threads\n") { 
     without_threads 
  }
  x.report("With threads\n") { 
     with_threads 
  }
end

You can compile JRuby programs with jrubyc command as below

jrubyc thread_cpu_bound.rb

Then you can execute program as (P.S. jruby-complete.jar can be used to run jruby compiled classes with Java)

java -cp ~/Downloads/jruby-complete-9.1.13.0.jar org.jruby.Main -S thread_cpu_bound.class