gistfile1.txt

class SpinnerDialog < Java::javax::swing::JDialog
  def initialize(parent=nil, modal=nil)
    unless parent.nil? && modal.nil?
      super
    else
      super()
    end
  end

  def position_to_center
    screen_size = java.awt.Toolkit.default_toolkit.screen_size
    self.set_location((screen_size.width - width) / 2, (screen_size.height - height) /2 )
  end
end
dialog = SpinnerDialog.new
dialog.position_to_center