hello_cytoscape.js

importPackage( Packages.javax.swing );

JOptionPane.showMessageDialog(
        null, "Hello Cytoscape!", "JavaScript on Cytoscape",
        Packages.javax.swing.JOptionPane.INFORMATION_MESSAGE
);

hello_cytoscape.rb

require 'java'

include_class 'javax.swing.JOptionPane'

JOptionPane.showMessageDialog(
        nil, "Hello Cytoscape!", "JRuby on Cytoscape",
        JOptionPane::INFORMATION_MESSAGE)