RFR: 8315999: Improve Date toString performance [v2]

[温绍锦]

On Mon, 11 Sep 2023 14:42:33 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> this place doesn't need off++
>
> It was a suggestion, implicitly paired with removing ` + (year < 0 ? 1 : 0)` from line 2188.

The reason for not using off++ is that it can be executed out of order, which may result in better performance.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15658#discussion_r1321781354