About your last comment - c# was explicitly made similar to java (at least at first, it diverged in time but the basics are close to being a superset of java).

My first job using c# was in 2010, and I have been programming in java since 2002 at that point. I was productive pretty much since the first day & not because I'm a genius - c# is that similar to java...

I suspect that if you'd have hired a php or a python expert they would have taken more time to get used to java (not that that would have meant you shouldn't hire them!)