I saw a Java team do the second one in an order router (a system that connects to various exchanges and routes+translates orders for each exchange's requirements), and they wrote an interesting retrospective doc where they basically said it wasn't worth it - it caused a lot of trouble without giving a significant edge in performance. YMMV! That was around 2012.

Quite fitting in a thread about HFT that has already referenced game development as a parallel universe of similar techniques.

In the feature phone era, mobile phone games were written in Java (well, a subset: Java EE). Practically all games followed the same memory management strategy. They allocated the memory they needed during the early initialisation, and then never again during the actual runtime of the game. That was the only way to retain even a semblance of performance.