Are you writing everything with a so-called superoptimizer (because mind you, not even your hand-written assembly will be the fastest, hell, C++/Rust will likely beat it in the general case)? Because it has always been a tradeoff between programmer’s sanity-correctness-maintainability-productivity-performance, at the least. Java does very well on most of it, including performance — it will JIT compile code comparable to C, the reason for the performance discrepancy between the two is memory layout, which may or may not matter for the problem at hand.
In my experience, most (especially business) applications are absolutely not going through millions of data entries doing some local calculations over them, that part is delegated to a database. They either do some IO over them, or have much smaller element sizes.
Java has escape hatches even for handling some of the “millions-of-elements in a hot loop”, but for an AAA game engine it might not be the best choice, but for anything else? It is more than fair game.
Well I regularly do juggle millions of objects in Java. I'd estimate most Java application code is probably running at about a fifth the speed it could be. Modern computers are incredibly fast, but most of that speed is wasted copying data between representations and garbage collecting Stream API debris and boxed integers. Moreover, most Java applications using a database for storage do so in a dumb way that doesn't make good use of either the database or Java.
Well, as I mentioned there are escape hatches, but those come at a price in usually maintainability, e.g. using SoA, or external heap.
If you do have a million objects and it is indeed a performance bottleneck (as shown by the profiler) then it might be worthwhile to pursue these solutions, or even implementing them in another language. Noone claims that Java is for everything, but it is for most things.
