JRubyFXでコンストラクタに引数を渡しつつControllerを切り替える ref: http://qiita.com/supermomonga/items/20464ed426c7e4bdb7a4

application_controller.rb

class ApplicationController
  include JRubyFX::Controller

  def move klass, *args
    @stage.fxml klass, initialize: args
    @stage.show
  end

end

bar_controller.rb

class BarController < ApplicationController

  def initialize arg
    puts "I got `#{arg}` as a constructor argument!"
  end

  def click_button
    move FooController, "Hello, Foo!"
  end

end

foo_controller.rb

class FooController < ApplicationController

  def initialize arg
    puts "I got `#{arg}` as a constructor argument!"
  end

  def click_button
    move BarController, "Hello, Bar!"
  end

end