UML in BlueJ and Eclipse

Unified Modeling Language ( UML ) is the best way to design an application and to analyze an object oriented code.

Taking a code and easily turn it into a UML can be done with an IDE, but there are extensions for IDEs that do not support UML generation by default.  BlueJ has two extensions that can be used for this purpose.

BlueJ UML extensions video if you need it
https://youtu.be/e5h15mTvEP4

Copy the jar files into folder <BLUEJ_HOME>\lib\extensions

Class Card - A Better UML Extension - http://klassenkarte.steinhuber.de/
Con: No datatypes for attributes and parameters
Pro: Shows attributes

UML Extension - http://www.bluej.org/extensions/extensions.html 
Con: No attributes listed
Pro: Parameter and return value data types

 After adding the extensions, they will be available by right-clicking on the class you need to see its UML.

You can see the difference between the two extensions and decides witch one works for you.

At the end, you'll see that Eclipse does a much better job showing the UML based outline of the class and if you don't really need pretty graphics based UML, it will be the most complete UML with the least effort.