RFR: JDK-8074003 java.time.zone.ZoneRules.getOffset(java.time.Instant) can be optimized

[Stephen Colebourne]

One additional change is needed. The compareTo() method can rely on
the new epochSecond field as well.
Otherwise good!
Stephen


On 27 April 2015 at 17:24, Peter Levart <peter.levart at gmail.com> wrote:
> Hi again,
>
> Here's another optimization to be reviewed that has been discussed a while
> ago (just rebased from webrev.01) and approved by Stephen:
>
> http://cr.openjdk.java.net/~plevart/jdk9-dev/ZoneOffsetTransition.epochSecond/webrev.02/
>
>
> The discussion about it is intermingled with the ZoneId.systemDefault()
> discussion and starts about here:
>
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-February/031873.html
>
>
> The rationale for the optimization is speeding-up the conversion from epoch
> time to LocalDateTime. This conversion uses ZoneRules.getOffset(Instant)
> where there is a loop over ZoneOffsetTransition[] array that searches for
> 1st transition that has its toEpochSecond value less than the Instant's
> epochSecond. This calls ZoneOffsetTransition.toEpochSecond repeatedly,
> converting ZoneOffsetTransition.transition which is a LocalDateTime to
> epochSecond. This repeated conversion is unnecessary, as
> ZoneOffsetTransition[] array is part of ZoneRules which is cached.
> Optimizing the ZoneOffsetTransition implementation (keeping both
> LocalDateTime variant and eposhSecond variant of transition time as the
> object's state) speeds up this conversion.
>
>
> Regards, Peter
>