Starting school next month; have to choose Java or C# track

So based off of almost every article I've come across about the future of Java and C#, it seems that these languages are equally well in-demand, sought after, have solid foundations/support, and most importantly aren't going anywhere.

But, according to the TIOBE index charts Java vs C# it seems as if Java actually is in decline. Everybody out there says that Java is not going anywhere but what explains the decline over the past two decades?