I have to create a desktop application (.exe) where I can use Java swing. The backend code for performing some database operations are written in Java. It will be easy to write the UI in Swing but I want to know if there is something better available than Swing which will look much better than the Swing UI.
Can I use Flex? Can it be easily merged with Java code. Please suggest if any one know any other better options to develop this application.
Currently I would say your best bet is JavaFX2 (this comes with the latest Java 7 releases). This offers a rich modern user interface, and you construct it in Java (optionally combined with XML). JavaFX2 is Oracles official replacement of AWT/Swing, which will not be developed any further.
This image (taken from Oracle documentation) provides some examples.