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

Martin Buchholz martinrb at google.com
Tue Apr 2 18:33:41 UTC 2013

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.

More information about the core-libs-dev mailing list