Re: I suspect there are quite a few Java devs out there
If its their first and only language then most probably (but not certainly) not many. Languages are very closely tied to methodologies and seem to tie people into a certain way of thinking about how to solve the problem. People solve problems with the tools they are familiar with - that bloke solved Fermi's last theorem in 100 odd pages where Fermi couldn't quite fit his answer in the margin of his book, Different languages tend to take different approaches to things some will go from A to D via B and C and others via F G and H. My memories of Java were it went from A to B via A1, A2, A3 and A4 for a lot of the time but that may have been just my A and B were not in Java at the time.
If you try and learn other languages you will move into other problem spaces the languages were designed to solve and realise that problem space is not the same as language space and no language fits all but more importantly learn there are many ways to skin a cat and when it boils down to it when you have a job the best way to do it is the way the local cat skinners do it for the local cats and even after 50 years in the job you will still be learning shit your computer language has trouble with because it was designed by some anal retentive genius who had a problem with brackets or camel case or something else really irrelevant to a CPU or GPU, or in the case of Java by a committee of them.
All computer languages are shit but some people can at least drive them off road for a bit before they need a sky hook to get them out of trouble,