Von http://www.objectaid.com/:
The ObjectAid UML Explorer is an agile and lightweight code visualization tool for the Eclipse IDE. It shows your Java source code and libraries in live UML class and sequence diagrams that automatically update as your code changes. The image below is a class diagram of actual source code; click on it to see the editor in the Eclipse Java Perspective
Ein kleines HOWTO unter http://fuzz-box.blogspot.de/2012/09/how-to-generate-uml-diagrams-from-java.html?m=1.