Best practice for creating millions of small temporary objects

Run the application with verbose garbage collection:

java -verbose:gc

And it will tell you when it collects. There would be two types of sweeps, a fast and a full sweep.

[GC 325407K->83000K(776768K), 0.2300771 secs]
[GC 325816K->83372K(776768K), 0.2454258 secs]
[Full GC 267628K->83769K(776768K), 1.8479984 secs]

The arrow is before and after size.

As long as it is just doing GC and not a full GC you are home safe. The regular GC is a copy collector in the ‘young generation’, so objects that are no longer referenced are simply just forgotten about, which is exactly what you would want.

Reading Java SE 6 HotSpot Virtual Machine Garbage Collection Tuning is probably helpful.