8361717: Refactor Collections.emptyList() in Locale related classes

[naotoj]

Replaced Collections.emptyList() with List.of() as part of refactoring. This was discussed in the context of investigating a CDS-related issue (https://bugs.openjdk.org/browse/JDK-8357281?focusedId=14796714&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14796714). Although the root cause was ultimately determined to be user error, modernizing the code by using List.of() is still a desirable improvement

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Issue

• JDK-8361717: Refactor Collections.emptyList() in Locale related classes (Bug - P4)

Reviewers

• Brian Burkhalter (@bplb - Reviewer)
• Justin Lu (@justin-curtis-lu - Committer)
• Chen Liang (@liach - Reviewer)
• Christian Stein (@sormuras - Committer)

Reviewing

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[openjdk]

@naotoj This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8361717: Refactor Collections.emptyList() in Locale related classes

Reviewed-by: bpb, jlu, liach, cstein

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At the time when this comment was updated there had been 32 new commits pushed to the master branch:

• 2a53f5a: 8361754: New test runtime/jni/checked/TestCharArrayReleasing.java can cause disk full errors
• f67e435: 8361447: [REDO] Checked version of JNI ReleaseArrayElements needs to filter out known wrapped arrays
• c28bb8b: 8361647: Report the error reason on failed semaphore calls on macOS
• ... and 29 more: https://git.openjdk.org/jdk/compare/fa32bfe11300fdadb35f083037f6ab2a8985d210...master

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• i18n

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[mlbridge]

Webrevs

• 00: Full (b349e27b)

[bplb]

Looks fine.

[justin-curtis-lu]

Looks good. Thanks for fixing this.

[jdlib]

modernizing the code by using List.of() is still a desirable improvement

except that Collections.emptyList() and List.of() unfortunately have different tolerance to calls List.indexOf(null) and List.contains(null).

[liach]

Both lists aren't returned to users, so their null-hostile contains behavior has no impact.

[liach]

An effort #25922 exists to make the AOT/CDS requirements more obvious to core libraries. Hope we can have this easier down the road.

[naotoj]

Thanks for the reviews!

except that Collections.emptyList() and List.of() unfortunately have different tolerance to calls List.indexOf(null) and List.contains(null).

True in general, but as @liach mentioned, those singletons are internal use only so the difference is not relevant here.
/integrate

[openjdk]

Going to push as commit f5afbbd.
Since your change was applied there have been 40 commits pushed to the master branch:

• cbc7090: 8359809: AttributeList, RoleList and UnresolvedRoleList should never accept other types of Object
• f735275: 8361839: Problemlist BogusFocusableWindowState due to failures in the CI pipeline
• 3d37c4e: 8361693: Remove Klass::clean_subklass_tree()
• ... and 37 more: https://git.openjdk.org/jdk/compare/fa32bfe11300fdadb35f083037f6ab2a8985d210...master

Your commit was automatically rebased without conflicts.

[openjdk]

@naotoj Pushed as commit f5afbbd.

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