JEP 280 (Indify String Concat) integration

Peter Levart peter.levart at
Fri Jan 22 14:44:41 UTC 2016

Hi Aleksey,

Good work. Nice to see this integrated.

If StringConcatException ever gets thrown, will it propagate out of the 
concatenation expression execution? If yes, then it should probably be 
an unchecked exception, right?

Regards, Peter

On 01/22/2016 10:31 AM, Aleksey Shipilev wrote:
> Hi,
> I think it is time to integrate JEP 280 ("Indify String Concat") into JDK 9:
> The JEP is Targeted, the CCC is approved, the code reviews and
> pre-integration checks come clean. In theory, we would like to integrate
> with some "optimal" concat strategy switched by default, but we have to
> wait for some Hotspot compiler changes to settle before we can make that
> call. (Notably,
> So, I would like to proceed in two parts:
>   Part 1: Integrate all code changes, but keep the concatenation strategy
> to be the same "naive" StringBuilder.append chains. In other words, we
> are emitting string concat indy, but always link in the naive
> StringBuilder.append code.
>   Part 2: (After HS changes settle in) Re-run performance tests, and
> switch to a more optimal concatenation strategy. This amounts to
> one-liner change in a default value for Java property.
> Thoughts? I would like relevant Project Leads / Reviewers (langtools and
> jdk) to OKay the integration.
> FTR, the webrevs:
> Thanks,
> -Aleksey

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