24 of those files are under 100 lines - some of them are as small as three lines of code. and that's not a personal preference - that's mandated by Java that each type needs to be in its own file, ridiculous.
I don't see that as a problem at all, just like I don't see header files in C++ as a major problem, there are benefits as well and Java has the best IDEs of any language I've worked in except maybe SmallTalk.
Java has the best IDEs, because as a language development is essentially impossible without one. contrast with Go where I can put as many types into one file as I like, and I can (and do) use Go without an IDE, both personally and professionally
What part of Java development is impossible without an IDE?
It's a stupidly simple language.
Just because people actually use it and thus IDEs were developed to aid the development process doesn't make it a necessity at all. I have programmed Java countless times from vim without any plugins. The only pain point is imports, which would be similarly painful in any other language ever created.