RFR: 8310241: OffsetDateTime compareTo redundant computation

[Naoto Sato]

On Thu, 22 Jun 2023 19:03:03 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

> Remove a redundant comparison in java.time `OffsetDateTime.compareTo()`. 
> If the `compareInstant` utility method returns 0 (equal), it compares the `LocalDateTime`.
> However, `compareInstant` has already done that comparison; if it found equal, the `compareTo` method unnecessarily does it again.
> The code is refactored in `compareInstant` to do the comparison of `LocalDateTime` exactly once, if it is needed.
> 
> This case is covered by existing tests in test/jdk/java/time/tck/java/time/TCKOffsetDateTime.java

src/java.base/share/classes/java/time/OffsetDateTime.java line 173:

> 171:      * to distinguish them. This step is needed to make the ordering
> 172:      * consistent with {@code equals()}.
> 173:      *

This method is also called from the public `timeLineOrder()` method. Could this change cause a different order?

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PR Review Comment: https://git.openjdk.org/jdk/pull/14618#discussion_r1242593059