I'm a Java developer. I have a decade of experience doing that.
Why are all these companies hiring .Net developers not even giving me a chance at an interview? It's all computer programming. They're discriminating against me!
That's more a function of IT outsourcing hiring to HR. HR asked for requirements. IT replied with what it's currently using. HR doesn't have the domain-specific knowledge that would indicate that most anyone worth a damn can pick up a new language fairly easily, so if your resume says C++ when they're looking for C#, it gets circular-filed by HR.
(I got lucky with my current job...was referred to the director of IT by one of his acquaintances, so HR only got involved after the decision had already been made to hire me. I went from doing streaming video/audio with C++, DirectX, and our own compression algorithms to doing business-specific web apps with C#, ASP.NET, and SQL Server...rather a different skill set, but that's the kind of adaptability that the HR droids never take into account.)