netbeans 7.1 uml diagram generation from code

Add a new configuration to update centers: Tools -> Plugins -> Settings -> Add

As the URL copy the following into the textbox: http://dlc.sun.com.edgesuite.net/netbeans/updates/6.9/uc/m1/dev/catalog.xml

Now on the tab Available Plugins there should be UML in category UML. Install the plugin, and its done..!!