Except that it's quite literally impossible to ensure data-independent timing in Java - or, for that matter, in any language that does optimizations without a w

Except that it's quite literally impossible to ensure data-independent timing in Java - or, for that matter, in any language that does optimizations without a way to disable them. Yes, this includes standard-compliant C / C++, ironically enough. JITters are especially bad for this - what is data-independent today may not be data-independent tomorrow. Or even in a couple minutes when it decides to re-optimize. You ultimately have to dip down to assembly, or something that can be relied on to not do data-dependent optimizations, to ensure resilience against timing attacks. JNI can work, as can inline assembly in things like C / C++, or specifying compilers. But that's just punting things to another language. And you lose portability, among other things. Or worse, you end up with something that looks like language X, and is valid code in language X, but breaks evilly if it's ever run as though it was in language X.