Five to seven years ago, Java versus .Net was a hot topic. At that time, many organizations were at this important crossroad. Now, they have all made up their minds. But some are reconsidering their previous decision.
Putting it very briefly, .Net currently is more common in smaller, front-end projects, where integration with the desktop is essential, while Java is more common in larger, back-end projects, where legacy platforms run the core business applications and where integration with legacy systems is crucial.