RFR JDK-7143928 : (coll) Optimize for Empty ArrayList and HashMap

[Martin Buchholz]

On Tue, Apr 2, 2013 at 11:24 AM, Mike Duigou <mike.duigou at oracle.com> wrote:

>
> On Apr 2 2013, at 10:55 , Martin Buchholz wrote:
>
> > Thanks for the research.
> > It seems like hotspot is recognizing and optimizing fill loops, rather
> than
> > intrinsifying calls to Arrays.fill itself (good!).
>
> Why wouldn't doing both be better?
>
>
If hotspot recognizes and optimizes fill loops, Arrays.fill is optimized
"for free".


> > Anyways, I'd still like the "simple" fill loops in ArrayList to stay
> > unchanged.  Using Arrays.fill is only slightly more readable.
>
> Part of the goal of the change was to make the intent clearer. I'll
> improve the comments instead.


ArrayList is one of those classes that are important for educational
reasons.  Studying it will be part of many peoples' university education.
 So I applaud efforts to improve clarity.  But I think the fill loops are
sufficiently clear as they stand.