JEPs proposed to target JDK 9 (2015/7/16)

Vitaly Davidovich vitalyd at
Fri Jul 17 00:32:32 UTC 2015

Varhandles JEP talks about replacing Unsafe array accesses and trying to be
smarter about range check elimination to match performance of check-less
accesses using Unsafe today.  One use case that will suffer is parallel
arrays of equal length.  The programmer knows they're all the same length
(e.g. arrays are final fields allocated in ctor), and a handwritten check
for one suffices for the others; the accesses can then be safely done using
Unsafe with no range checks.  With varhandles, the JIT is not going to be
able to see this relationship between them and will issue range checks on
all accesses.

Has such a use case been discussed/thought about?

sent from my phone
On Jul 16, 2015 5:56 PM, <mark.reinhold at> wrote:

> The following JEPs have been placed into the "Proposed to Target"
> state by their owners after discussion and review:
>   193: Variable Handles
>   244: TLS Application-Layer Protocol Negotiation Extension
> Feedback on these proposals is more than welcome, as are reasoned
> objections.  If no such objections are raised by 22:00 UTC next
> Thursday, 23 July, or if they're raised and then satisfactorily
> answered, then per the JEP 2.0 process proposal [1] I'll target
> these JEPs to JDK 9.
> (This information is also available on the JDK 9 Project Page [2]).
> - Mark
> [1]
> [2]

More information about the jdk9-dev mailing list