Generational GC - particularly with escape analysis - can make those temp objects just slightly more expensive than stack allocation.
The odd thing about GenGC is that it punishes you for trying to recycle old objects yourself. You create much more pressure to scan the old generation by doing so, which is expensive. If you have the available memory it’s often better to build a new object and swap it for the retained reference to the old one at the end when you’re done (poor man’s MVCC as well if the switch takes a couple context switches to finish)
The odd thing about GenGC is that it punishes you for trying to recycle old objects yourself. You create much more pressure to scan the old generation by doing so, which is expensive. If you have the available memory it’s often better to build a new object and swap it for the retained reference to the old one at the end when you’re done (poor man’s MVCC as well if the switch takes a couple context switches to finish)