AgileJ StructureViews code visualizer for Eclipse is:
1 Specialized for Reverse Engineered Diagrams - more akin to an extension to the Eclipse Java browsing perspective than a drawing tool.
2 Dedicated to Java - exceptions, inner classes and Javadoc all influence the diagrams.
3 Focused on Class Diagrams - because they can be made self-populating and self-updating, playing a long-term role in an Agile/XP project.
4 Tightly Integrated into Eclipse - the diagram nomenclature follows that of Eclipse, resulting in the lowest switching overhead between looking at diagrams and looking at Eclipse.
5 Filtered by Customized Rules - diagrams are tuned to highlight one aspect, dimension, concern or technology at a time.
For more detail: http://www.agilej.com/
Recommend the tutorial