Also, once you have learned Java, you don't have far to go to also learn C#. Most of the differences with C# are solutions to problems that have not yet been fixed in Java, i.e. C# is faster moving from a language design point of view. Yes, the .Net libraries are completely different, but few software developers nowadays bother to learn a set of libraries inside out because reference material and search engines are so much better than they were a few years ago.