Which optimizations does Hotspot apply?

Vitaly Davidovich vitalyd at gmail.com
Fri Jan 24 22:01:49 UTC 2014

This would be predicated on escape analysis, whose effectiveness is in turn
driven by sufficient inlining whereby compiler can see that instance
doesn't escape.  Inlining, in turn, can be screwed up by (amongst other
things) polymorphic call sites.  So in the end, it's all quite brittle and
sensitive :).  Personally, in places where it matters, I try to allocate as
little as possible explicitly - a lot of times much more effective than
hoping compiler helps out and/or turning GC knobs.

Sent from my phone
On Jan 24, 2014 4:36 PM, "Andrej Golovnin" <golovnin at gmx.net> wrote:

> Hi Rémi,
> > With latest jdk8, it's not true anymore.
> > (and most of the time the iterator object is not created anymore at
> least with jdk7+).
> Could you please explain it a little bit more? When is that optimization
> applied,
> e.g. what conditions are required for this optimization, since which
> version
> of JDK/Hotspot it is supported, where it is implemented in JDK?
> When I take look at a product I'm working on, I see a lot instances of
> ArrayList$Itr objects,
> which are created by for-each loops (we use JDK 7u51).
> Thanks in advance!
> Best regards,
> Andrej Golovnin

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