Author of: Getting started with Java programming language | Getting started with Spring Framework | Portlets in Action | Spring Roo 1.1 Cookbook | Portlets blog | Spring Roo blog
<a href="http://www.zeroturnaround.com/jrebel/" target="_blank" rel="nofollow">JRebel</a> reloads Java code on-the-fly (<a href="http://www.zeroturnaround.com/jrebel-demonstration-screencast/" target="_blank" rel="nofollow">see demo screencast</a>)