RFR: 8355522: Remove the `java.locale.useOldISOCodes` system property [v5]

[Andrey Turbanov]

On Mon, 8 Dec 2025 19:08:46 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> This PR removes the system property deprecated in JDK 25. If the property is specified at runtime, a warning will be emitted at startup to inform the user that the value is ignored. A corresponding CSR has been drafted as well
>
> Naoto Sato has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:
> 
>  - Reflects review comments
>  - Merge branch 'master' into JDK-8355522-Remove-useOldISOCodes
>  - Further wording refinement
>  - Obsolete comment correction
>  - Reflects review comments
>  - initial commit

src/java.base/share/classes/sun/util/locale/BaseLocale.java line 116:

> 114:      */
> 115:     static {
> 116:         if (!System.getProperty("java.locale.useOldISOCodes", "").isEmpty()) {

Hm. Why don't we compare result with null? Do we want to allow empty values `-Djava.locale.useOldISOCodes=` ?

Suggestion:

        if (System.getProperty("java.locale.useOldISOCodes") != null) {

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PR Review Comment: https://git.openjdk.org/jdk/pull/26419#discussion_r2600000217