RFR: 8364320: String encodeUTF8 latin1 with negatives

[Chen Liang]

On Fri, 1 Aug 2025 12:34:15 GMT, Brett Okken <duke at openjdk.org> wrote:

> As suggested on mailing list, when encoding latin1 bytes to utf-8, we can count the leading positive bytes and in the case where there is a negative, we can copy all the positive values to the target byte[] prior to processing the remaining data 1 byte at a time.
> 
> https://mail.openjdk.org/pipermail/core-libs-dev/2025-July/149417.html

src/java.base/share/classes/java/lang/String.java line 1297:

> 1295:         }
> 1296:         int dp = positives;
> 1297:         for (int i=dp; i<val.length; ++i) {

Suggestion:

        for (int i = dp; i < val.length; ++i) {

Though we usually use `i++` more often, `++i` should be fine too.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26597#discussion_r2247915445