alt Hacker NewsI need a UI which runs well on Windows, MacOS, and Linux, without having to build three different ones. Swing is still easily the best, most consistent, and most native-feeling cross-platform environment. It's much better than QT and GTK in most respects. And Java also runs elegantly on a little platform you may know as Android. I have high hopes for go and rust. But until they have mature UIs, they're out (for me).
C and C++ are dangerous languages filled with security failings and footguns, and no modern app should be written in them.
It's been my experience that well-written low-level Java code runs at about 75% the speed of good C code. (Of course lazy coders write in cushy Java which is much slower). When written efficiently, Java's biggest slowdown lies in array access (C and C++ array access is fast because it is very, very unsafe). But Java makes up for this in having a GC which will coalesce related objects into the same page and so take advantage of cache coherency effects in ways malloc and free cannot possibly do. I have some allocation-heavy algorithms in Java which are, as a result, significantly faster than well-written equivalents in C.
In heavily performance-engineered code having a GC coalesce memory is a pessimization in all cases.
I've done a lot of performance engineering in both C++ and Java. Every optimization available in Java also exists in C++ but the reverse is not true, which is why C++ is always faster. Every example I have ever seen of Java being faster than C++ was just poorly optimized code. The heuristic I use is that heavily optimized C++ is about twice as fast as heavily optimized Java at the limit. And this requires some non-idiomatic and ugly Java that isn't nice to maintain.
This doesn't necessarily make Java the wrong choice though. Few organizations prioritize absolute performance above all other things. There are practical tradeoffs.