8379337: Deprecate Modifier.toString by liach · Pull Request #30093 · openjdk/jdk

liach · 2026-03-05T17:54:14Z

In project valhalla development, we discovered that Modifier.toString becomes more problematic than helpful: there's now a mix-and-match of modifiers from access flags and other class file sources, for example, classes now can have ACC_IDENTITY, which clashes with ACC_SYNCHRONIZED, and the correct modifier to reflect, "value", must be deduced by the users manually.

With fewer bits available for the access flags, it becomes more apparent that future source modifiers will no longer be reflected by Modifier.toString, and future access flags are more likely to be reflected incorrectly. Thus, we should dissuade users from this API in the long run.

I confirm that I make this contribution in accordance with the OpenJDK Interim AI Policy.

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Change requires CSR request JDK-8379338 to be approved

Issues

JDK-8379337: Deprecate Modifier.toString (Bug - P4)
JDK-8379338: Deprecate Modifier.toString (CSR)

Reviewers

Alan Bateman (@AlanBateman - Reviewer)

Reviewing

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Using Webrev

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…ecate-modifier-tostring

bridgekeeper · 2026-03-05T17:55:24Z

👋 Welcome back liach! 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 · 2026-03-05T17:55:41Z

@liach 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:

8379337: Deprecate Modifier.toString

Reviewed-by: alanb

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 12 new commits pushed to the master branch:

635c4b9: 8377727: Ghost caret and focus appear in non‑editable text fields
2fe7ae9: 8381362: C2: assert(_late_inlines.length() == 0 || IncrementalInlineMH || IncrementalInlineVirtual) failed: not empty
6b6f299: 8382316: Unused xtmp in long_to_maskLE8_avx
... and 9 more: https://git.openjdk.org/jdk/compare/832bd9cdc37e89cd851e71dfb3a217994600bb25...master

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openjdk · 2026-03-05T18:00:02Z

@liach The following labels will be automatically applied to this pull request:

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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 · 2026-03-05T18:03:17Z

Webrevs

ExE-Boss · 2026-03-09T16:42:00Z

+ *     have a corresponding access flag</li>
+ * <li>The same bit may represent different flags in different structures, like
+ *     {@code 0x0040} represents {@link #VOLATILE ACC_VOLATILE} in fields and
+ *     {@code ACC_BRIDGE} in interfaces</li>


ACC_BRIDGE applies to all bridge methods, not only those on interfaces.

Suggested change

* {@code ACC_BRIDGE} in interfaces</li>

* {@code ACC_BRIDGE} in methods</li>

Marcono1234

Hopefully these review comments are useful. Feel free to only consider them as suggestions.

Marcono1234 · 2026-03-13T14:59:39Z

+ * </ol>
+ * These assumptions are no longer valid:
+ * <ol>
+ * <li>Java language modifiers like method modifier {@code default} does not


Maybe grammar issue: This refers to the plural "modifiers"

Suggested change

* <li>Java language modifiers like method modifier {@code default} does not

* <li>Java language modifiers like method modifier {@code default} do not

Marcono1234 · 2026-03-13T15:00:10Z

+ *     {@code 0x0040} represents {@link #VOLATILE ACC_VOLATILE} in fields and
+ *     {@code ACC_BRIDGE} in interfaces</li>
+ * </ol>
+ * To mitigate, {@code Modifier} class only include source modifiers that


Maybe grammar issue

Suggested change

* To mitigate, {@code Modifier} class only include source modifiers that

* To mitigate, the {@code Modifier} class only includes source modifiers that

Marcono1234 · 2026-03-13T15:04:11Z

+     * objects, such as {@link Class#accessFlags()}.
+     * <p>
+     * To print an access flags value for debug output, consider using the
+     * format {@code %04x} instead of this method; this method omits all class


Maybe this should say "hex format" or similar to make it immediately obvious what this pattern does?

Suggested change

* format {@code %04x} instead of this method; this method omits all class

* hex format {@code %04x} instead of this method; this method omits all class

I used 'format' because you can use this out of the box in String.format, printf, and String.formatted. 'hex format' I'm afraid would make users think they need to use java.util.HexFormat, I haven't tried using that to print yet.

Marcono1234 · 2026-03-13T15:05:14Z

     * modifiers that can be applied to a class.
     *
+     * @deprecated
+     * This method is intended to be used in conjunction with {@link #toString()


Link to wrong toString method? toString() is not deprecated only toString(int)?

Suggested change

* This method is intended to be used in conjunction with {@link #toString()

* This method is intended to be used in conjunction with {@link #toString(int)

(same also below for all other occurrences)

AlanBateman · 2026-03-16T18:44:57Z

     * interface (JLS {@jls 9.1.1}).
     *
+     * @deprecated
+     * This method tries to describe the source modifiers from an access flags


I agree that the methods should be deprecated but I think the @deprecated text will need a few iterations. I think it would be better to start with something like "This method was originally specified to describe the source modifiers ..." rathe rthan "This tries ...".

AlanBateman · 2026-03-16T18:57:55Z

- * {@jls 9.4.3}) and the {@code sealed} and {@code non-sealed} class
- * (JLS {@jls 8.1.1.2}) and interface (JLS {@jls 9.1.1.4}) modifiers
- * are <em>not</em> represented in this class.
+ * {@code Modifier} was designed with two assumptions:


I think the apiNote will need a few iterations on the wording. I don't like it starting with the assumptions and then saying that the assumptions aren't valid. Instead I think it would be better to say that the translation of source modifiers to access flags has evolved since the API was originally introduced. In addition, the bit may represent different flags. The API can still be used for source modifiers that directly map to an access flag. New code is encouraged to use AccessFlags.

…ecate-modifier-tostring

bridgekeeper · 2026-04-14T03:05:04Z

@liach This pull request has been inactive for more than 4 weeks and will be automatically closed if another 4 weeks passes without any activity. To avoid this, simply issue a /touch or /keepalive command to the pull request. Feel free to ask for assistance if you need help with progressing this pull request towards integration!

openjdk · 2026-04-16T19:19:44Z

The total number of required reviews for this PR has been set to 2 based on the presence of this label: hotspot-compiler. This can be overridden with the /reviewers command.

liach · 2026-04-16T21:59:45Z

/template append
/label remove hotspot-compiler
/reviewers 1 reviewer

openjdk · 2026-04-16T22:01:50Z

@liach The pull request template has been appended to the pull request body

openjdk · 2026-04-16T22:02:51Z

@liach
The hotspot-compiler label was successfully removed.

openjdk · 2026-04-16T22:03:28Z

@liach
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 1 (with at least 1 Reviewer).

…ecate-modifier-tostring

Marcono1234 · 2026-04-19T14:26:40Z

+ * <p>
+ * Java SE 5.0 introduced many new access and property flags, such as {@link
+ * AccessFlag#SYNTHETIC ACC_SYNTHETIC}.  Unlike {@code ACC_SUPER}, these access
+ * and property flags are reported by the {@code getModifier()} methods.


Should this be getModifiers()?

Suggested change

* and property flags are reported by the {@code getModifier()} methods.

* and property flags are reported by the {@code getModifiers()} methods.

…ecate-modifier-tostring

openjdk · 2026-04-20T16:09:49Z

@liach hotspot-runtime has been added to this pull request based on files touched in new commit(s).

liach · 2026-04-20T17:06:54Z

/label remove hotspot-runtime

openjdk · 2026-04-20T17:07:36Z

@liach
The hotspot-runtime label was successfully removed.

…ecate-modifier-tostring

AlanBateman · 2026-04-22T13:08:11Z

+ * <p>
+ * Modifier interpretation is context-sensitive: for example, the bit checked by
+ * {@link #isSynchronized(int) isSynchronized} only represents the {@code
+ * synchronized} modifier on methods, so a {@code true} return on a field


The first paragraph uses "flags", the second paragraph switches to "bits", a term that is never used again. The referenced AccessFlags or javax.lang.model.element.Modifier doesn't speak of bits. So I'm wondering if it would be better to say "the modifier checked by ..." rather than "bit checked".

I will use "access flags" consistently.

AlanBateman · 2026-04-22T13:09:46Z

     *
+     * @deprecated
+     * This method exists solely to support the now-deprecated
+     * {@link #toString(int) Modifier::toString(int)} method.


What would think of changing the first sentence to "This method was originally created to the support ..". The second sentence is good, sends the reader to the new API.

AlanBateman

I think this is mostly looks good, just some minor word smithing on the docs change.

…ecate-modifier-tostring

liach · 2026-04-23T14:39:08Z

/integrate

Thanks for the reviews!

openjdk · 2026-04-23T14:40:21Z

Going to push as commit cb8860a.
Since your change was applied there have been 16 commits pushed to the master branch:

17e9151: 8382740: JFR: Disable jdk.OldObjectSample event for generational ZGC
e896c66: 8381939: G1: Fix marking state verification at the end of a concurrent start pause
18d8aa0: 8377655: C1: in x86, avoid 0x00s leftover after PatchingStub
... and 13 more: https://git.openjdk.org/jdk/compare/832bd9cdc37e89cd851e71dfb3a217994600bb25...master

Your commit was automatically rebased without conflicts.

openjdk · 2026-04-23T14:40:36Z

@liach Pushed as commit cb8860a.

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

liach added 2 commits February 6, 2026 18:18

Deprecate Modifier.toString

b614145

Merge branch 'master' of https://github.com/openjdk/jdk into fix/depr…

a882cd3

…ecate-modifier-tostring

openjdk Bot added hotspot-compiler hotspot-compiler-dev@openjdk.org core-libs core-libs-dev@openjdk.org compiler compiler-dev@openjdk.org labels Mar 5, 2026

openjdk Bot added csr Pull request needs approved CSR before integration rfr Pull request is ready for review labels Mar 5, 2026

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Merge branch 'master' of https://github.com/openjdk/jdk into fix/depr…

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…ecate-modifier-tostring

liach mentioned this pull request Apr 15, 2026

8380129: Remove AccessFlags::print_on in favor of context-specific printing #30746

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liach added 3 commits April 16, 2026 17:55

Merge branch 'master' of https://github.com/openjdk/jdk into fix/depr…

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…ecate-modifier-tostring

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Merge branch 'master' of https://github.com/openjdk/jdk into fix/depr…

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…ecate-modifier-tostring

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Merge branch 'master' of https://github.com/openjdk/jdk into fix/depr…

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…ecate-modifier-tostring

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liach added 3 commits April 22, 2026 09:14

Merge branch 'master' of https://github.com/openjdk/jdk into fix/depr…

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…ecate-modifier-tostring

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	* {@code ACC_BRIDGE} in interfaces</li>
	* {@code ACC_BRIDGE} in methods</li>

	* <li>Java language modifiers like method modifier {@code default} does not
	* <li>Java language modifiers like method modifier {@code default} do not

	* To mitigate, {@code Modifier} class only include source modifiers that
	* To mitigate, the {@code Modifier} class only includes source modifiers that

	* format {@code %04x} instead of this method; this method omits all class
	* hex format {@code %04x} instead of this method; this method omits all class

	* This method is intended to be used in conjunction with {@link #toString()
	* This method is intended to be used in conjunction with {@link #toString(int)

	* and property flags are reported by the {@code getModifier()} methods.
	* and property flags are reported by the {@code getModifiers()} methods.

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