This project is an interesting example of an application built using the Google Web Toolkit (GWT). Kelly and Miguel spent a Sunday afternoon prior to their tutorial at EclipseCon 2007 developing an instant messenger web application.

The source for Chattr is available in the Downloads section, and you can either get the 'complete' app version, or a version that is 'working.' The latter was intended for those people who were following along at the tutorial.

More about GWT, in case you're unfamiliar:

GWT is an open source Java development framework that lets you escape the matrix of technologies that make writing AJAX applications so difficult and error prone. 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.

To get started, download GWT.