I’m a software engineer for 20+ years working with Java and open source apps and in the cloud, and I can work in Win 7 (still available) or MAC just fine. MAC is less supportive of the latest versions of Java as well.
Not true, it works just like Windows. Apple just stopped supporting it directly, Oracle provides support instead. The same Java 8 is available for Mac, just download it from Oracle's site.
The Mac is extremely popular for software development. I'm aware of a large government software contract where a majority of developers are using Macs. Almost all the rest run Linux.
Windows is a second rate software development platform these days.