That's terribly ugly. Can they not do escape analysis or something to avoid allocations in obvious places? Or only allocate when the value is moved off the stack?
Doesn't Android use a different flavor of Java anyways, allowing them to make these changes?
Yes, it's possible in theory, but Dalvik/ART don't do it. HotSpot does some escape analysis and the Graal compiler for HotSpot does a much more advanced form called partial escape analysis, which is pretty close to ideal if you have aggressive enough inlining.
The problem Google has is that Dalvik wasn't written all that well originally. It had problems with deadlocking due to lock cycles and was sort of a mishmash of C and basic C++. But then again it was basically written by one guy under tight time pressure, so we can give them a break. ART was a from scratch rewrite that moved to AOT compilation with bits of JITC, amongst other things. But ART is quite new. So it doesn't have most of the advanced stuff that HotSpot got in the past 20 years.
Yes, this is why I always find sad that language performance gets thrown around in discussions forums without reference to what implementations are actually being discussed.
Doesn't Android use a different flavor of Java anyways, allowing them to make these changes?