Swing JButton ActionListener(Anonymous Inner Class) implicit closure conversion

JButtonActionListenerTest.rb

include Java

java_import java.awt.Dimension
java_import javax.swing.JPanel
java_import javax.swing.JButton
java_import javax.swing.JTextField

class MainPanel < JPanel
  def initialize
    super
    field = JTextField.new 32
    button = JButton.new "add a"
    button.add_action_listener { |e|
      puts e
      field.text = field.text + "a"
    }
    self.add field
    self.add button
    self.preferred_size = Dimension.new(320, 240)
  end
end

java_import javax.swing.UIManager
java_import javax.swing.WindowConstants
def create_and_show_GUI
  begin
    UIManager.look_and_feel = UIManager.system_look_and_feel_class_name
  rescue Exception => e
    proxied_e = JavaUtilities.wrap e.cause
    proxied_e.print_stack_trace
  end
  frame = javax.swing.JFrame.new "JRuby Swing JButton ActionListener"
  frame.default_close_operation = WindowConstants::EXIT_ON_CLOSE
  frame.content_pane.add MainPanel.new
  frame.pack
  frame.location_relative_to = nil
  frame.visible = true
end
def run
  create_and_show_GUI
end
java.awt.EventQueue.invokeLater self