8347949: Currency method to stream available Currencies #23165

justin-curtis-lu · 2025-01-16T22:21:26Z

Please review this PR and CSR which adds a method to java.util.Currency which returns a stream of the available Currencies.

The motivation can be found in the CSR.

Progress

Change must not contain extraneous whitespace
Commit message must refer to an issue
Change requires CSR request JDK-8347950 to be approved
Change must be properly reviewed (2 reviews required, with at least 2 Reviewers)

Issues

JDK-8347949: Currency method to stream available Currencies (Enhancement - P4)
JDK-8347950: Currency method to stream available Currencies (CSR)

Reviewers

Naoto Sato (@naotoj - Reviewer)
Chen Liang (@liach - Reviewer)
Roger Riggs (@RogerRiggs - Reviewer) Review applies to ade21c92

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/23165/head:pull/23165
$ git checkout pull/23165

Update a local copy of the PR:
$ git checkout pull/23165
$ git pull https://git.openjdk.org/jdk.git pull/23165/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 23165

View PR using the GUI difftool:
$ git pr show -t 23165

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Using Webrev

Link to Webrev Comment

bridgekeeper · 2025-01-16T22:22:29Z

👋 Welcome back jlu! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2025-01-16T22:22:49Z

@justin-curtis-lu This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8347949: Currency method to stream available Currencies

Reviewed-by: naoto, liach, rriggs

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 17 new commits pushed to the master branch:

cbe9ec5: 8348905: Add support to specify the JDK for compiling Jtreg tests
6b581d2: 8347997: assert(false) failed: EA: missing memory path
4662363: 8348687: [BACKOUT] C2: Non-fluid StringBuilder pattern bails out in OptoStringConcat
d266ca9: 8348752: Enable -XX:+AOTClassLinking by default when -XX:AOTMode is specified
cbc89a7: 8348898: Remove unused OctalDigits to clean up code
96fefed: 8319850: PrintInlining should print which methods are late inlines
51cce6e: 8318577: Windows Look-and-Feel JProgressBarUI does not render correctly on 2x UI scale
6bfae3a: 8333386: TestAbortOnVMOperationTimeout test fails for client VM
f98d9a3: 8348870: Eliminate array bound checks in DecimalDigits
fe6d9ab: 8348582: Set -fstack-protector when building with clang
... and 7 more: https://git.openjdk.org/jdk/compare/3a564ed1019c66c28afa729973948d3a6e6c4c41...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

openjdk · 2025-01-16T22:23:23Z

@justin-curtis-lu The following labels will be automatically applied to this pull request:

core-libs
i18n

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

mlbridge · 2025-01-16T22:26:09Z

Webrevs

naotoj

Looks good.

naotoj · 2025-01-17T22:11:51Z

src/java.base/share/classes/java/util/Currency.java

+    // Initialize the set of available currencies if needed
+    private static synchronized void initAvailableCurrencies() {
+        if (available == null) {
+            available = new HashSet<>(256);


Not related to your change, but this should be HashSet.newHashSet(256). In fact 256*0.75 is 192, which is smaller than the current number of currencies (230, as of JDK24)

Fixed in c94ba94

RogerRiggs · 2025-01-17T22:49:07Z

src/java.base/share/classes/java/util/Currency.java

+     * {@return a set of available currencies} The returned set of currencies
+     * contains all the available currencies, which may include currencies
+     * that represent obsolete ISO 4217 codes. If there is no currency available
+     * in the runtime, the returned set is empty. The set can be modified


An apiNote might be appropriate to refer/recommend using the new availableCurrencies() API.
And/or an @see link to the method.

Thanks Roger, incorporated both your suggestions in dcb4a9b. Note, I intentionally did not add any wording regarding the defensive copy in the apiNote, considering that is an implementation specific caveat.

RogerRiggs · 2025-01-17T22:53:13Z

src/java.base/share/classes/java/util/Currency.java

+     * available in the runtime, the returned stream is empty.
+     *
+     * @implNote Unlike {@link #getAvailableCurrencies()}, this method does
+     * not create a defensive copy of the {@code Currency} set.


An @see link to getAvailableCurrencies might be useful.

RogerRiggs · 2025-01-17T23:25:06Z

test/jdk/java/util/Currency/AvailableCurrenciesTest.java

+    @Test
+    public void streamEqualsSetTest() {
+        var currencies = Currency.getAvailableCurrencies();
+        assertEquals(currencies, Currency.availableCurrencies().collect(Collectors.toSet()));


Generally, a message describing the failure is more useful than just a stacktrace. (the 3rd arg on assertEquals override.)
It avoids needing to find the source code to create the bug report.

liach · 2025-01-18T01:29:01Z

src/java.base/share/classes/java/util/Currency.java

+    }
+
+    // Initialize the set of available currencies if needed
+    private static synchronized void initAvailableCurrencies() {


Should we make available volatile so we can avoid entering the monitor if the currencies are initialized?

(Note: We may get Stable Values very soon, at that point SV is a much better solution)

Thanks Chen, made available volatile and implemented DCL in 96e86c8.
Also added a duplicate elements test as you suggested.

I'm not sure how useful it is to optimize the performance of availableCurrencies access to "available", but adding volatile will slow every access down.
The computation of the available currencies is stable, so a race computing it is benign.
Except for the available hashSet being partially filled when read by the thread calling getAvailableCurrencies().
That could be remedied by using a new local for the new HashSet in initAvailableCurrencies and assigning to available only when the set is completely initialized.
(And yes, this looks like a good fit for stable values.)

How about I revert the most recent commit and have this PR simply deliver the change to provide the stream of currencies. I'll file another issue to improve available to use stable values when that is available. Does that sound fine?

Reverted in ade21c9. Filed JDK-8348351 to implement available as a stable value when applicable.

I suspect that Stable Values would fit well here.

liach · 2025-01-18T01:34:20Z

test/jdk/java/util/Currency/AvailableCurrenciesTest.java

+        var currencies = Currency.getAvailableCurrencies();
+        assertEquals(currencies, Currency.availableCurrencies().collect(Collectors.toSet()),
+                "availableCurrencies() and getAvailableCurrencies() do not have the same elements");
+    }


Should we add a test to ensure Currency.availableCurrencies() has no duplicate elements?

Currency.availableCurrencies().collect(Collectors.toMap(Function.identity(), Function.identity());

viktorklang-ora · 2025-01-20T09:46:05Z

src/java.base/share/classes/java/util/Currency.java

+                        SpecialCaseEntry scEntry = specialCasesList.get(index);
+
+                        if (scEntry.cutOverTime == Long.MAX_VALUE
+                                || System.currentTimeMillis() < scEntry.cutOverTime) {


It'd be better to obtain the current time once and compare against the same value for all entries rather than potentially using different current times for each comparison.

That's a good point. I filed JDK-8348205 because that change would have its own behavioral concerns, which I don't want to overlap with this issue/CSR.

liach

The PR looks good in the current form. Since I am no professional in locale area, requesting another review from Naoto or Roger.

/reviewers 2 reviewer

openjdk · 2025-01-28T16:08:50Z

@liach
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 2 Reviewers).

naotoj

We could add @stable to available for now, but forseeing the stable values, not that significant. So fine by me as in its current form

RogerRiggs

lgtm

openjdk · 2025-01-28T21:59:14Z

@justin-curtis-lu this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout 8347949-Currency-Stream
git fetch https://git.openjdk.org/jdk.git master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

justin-curtis-lu · 2025-01-30T17:55:15Z

Thanks all for the reviews.
/integrate

openjdk · 2025-01-30T17:55:50Z

Going to push as commit f05c53c.
Since your change was applied there have been 36 commits pushed to the master branch:

cc775b1: 8348648: Unnecessary Hashtable usage in javax.swing.text.html.CSS.LengthUnit
06ebb17: 8349002: GenShen: Deadlock during shutdown
1ac2d6e: 8349009: JVM fails to start when AOTClassLinking is used with unverifiable old classes
0cae888: 8349003: NativeCallStack::print_on() output is unreadable
fdfb68c: 8344168: Change Unsafe base offset from int to long
5d5b294: 8349070: Fix riscv and ppc build errors caused by JDK-8343767
3f8a875: 8348880: Replace ConcurrentMap with AtomicReferenceArray for ZoneOffset.QUARTER_CACHE
fac63d4: 8348668: Prevent first resource cleanup in confined arena from escaping
2efb6aa: 8345314: Add a red–black tree as a utility data structure
a937f6d: 8343767: Enumerate StubGen blobs, stubs and entries and generate code from declarations
... and 26 more: https://git.openjdk.org/jdk/compare/3a564ed1019c66c28afa729973948d3a6e6c4c41...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-01-30T17:55:57Z

@justin-curtis-lu Pushed as commit f05c53c.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

init

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openjdk bot added csr Pull request needs approved CSR before integration rfr Pull request is ready for review labels Jan 16, 2025

openjdk bot added core-libs [email protected] i18n [email protected] labels Jan 16, 2025

synchronize init method over block

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naotoj reviewed Jan 17, 2025

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init hashset w/ accurate size via HashSet.newHashSet(int)

c94ba94

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reflect Roger's review

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provide message for test assertion

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justin-curtis-lu added 2 commits January 21, 2025 10:09

reflect feedback

96e86c8

Merge branch 'master' into 8347949-Currency-Stream

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openjdk bot removed the csr Pull request needs approved CSR before integration label Jan 22, 2025

make 'available' un-volatile

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8347949: Currency method to stream available Currencies #23165

8347949: Currency method to stream available Currencies #23165

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8347949: Currency method to stream available Currencies #23165

8347949: Currency method to stream available Currencies #23165

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