Is there any documentation available which optimizations Hotspot can perform
and what "collecting a garbage" object costs?
I know that these are two completely different areas ;)
I was inspecting whether the following code
for (Object o : someArrayList) { ... }
would be faster than
for (int i=0, l=someArrayList.size(); i<l; i++) { Object
o=someArrayList.get(i); }
for RandomAccessList implementations. The challenge here is not just to track
the CPU time spent creating & using the iterator vs. size() & get() calls but
also track GC effort (which is at least complicated if not impossible due to
the variety of GC configuration options).
For example:
- Does it help Hotspot to declare parameters/variables as "final" or can
Hotspot identify that?
- When does Hotspot inline method calls in general and getters/setters
especially?
I think such a piece of documentation (just what Hotspot can do in which
release) would be really helpful when someone tries to optimize code - want to
say: the question is: "Is something worth to spend time on or is this special
situation handled by Hotspot?"
-Robert
