I think I understand this. I don't know Java, but I understand the premise here.
Link: Google Code Blog: Write AJAX applications in the Java language with Google Web Toolkit.
Google Web Toolkit (GWT) is a Java software development framework that makes writing AJAX applications easy. With GWT, you can develop and debug AJAX applications in the Java language using the Java development tools of your choice. When you deploy your application to production, the GWT compiler translates your Java application to browser-compliant JavaScript and HTML.
