Astah Community Edition
Today’s object oriented languages require extensive use of objects, their inter-relationships and methods. There are several UML tools out there like UMlet, Umbrello on Linux, but this one from astah stands out. You can try the community edition before deciding to purchase a full version. It enables the creation of objects, building their relations and then using those to generate code in any object oriented language like C++ or Java. Some of the tools offer plug-ins into IDEs like Eclipse and Netbeans. See astah for yourself.
Install the rpm file and execute the program using:
$ astah-com <enter>
You can also try another tool called Modelio. You can download it from http://www.modelio.org. It is written in Java and is as easy as astah. The only benefit with Modelio is that it is free.