JEP 401: Value Objects (Preview) merged to OpenJDK master

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openjdk / jdk Public Notifications You must be signed in to change notification settings Fork 6.4k Star 23.2k Conversation MrSimms commented May 11, 2026 • edited by openjdk Bot Loading Uh oh! There was an error while loading. Please reload this page .

Copy link Copy Markdown Member This pull request implements the first preview of JEP 401: Value Objects (Preview) . This pull request also includes the implementation of JEP 539: Strict Field Initialization in the JVM (Preview) . That work was implemented in the same code base because JEP 401 depends on strict field initialization.

Sub-reviews, for spreading review debates are here:

8317277: Java language implementation of value objects #31121 JDK-8317278 : JVM implementation of value objects 8317278: JVM implementation of value objects #31122 JDK-8317279 : Standard library implementation of value objects 8317279: Standard library implementation of value objects #31123 This is the " master pull request " for the initial preview of JEP 401 . Comments and review for a change this large will not scale well in a single pull request. This pull request serves as the vehicle for sign-off and integration into jdk/master . Review comments should be directed to the appropriate " sub-review pull request " listed above.

The " sub-review pull requests " contain the same full set of code changes as this " master pull request " to preserve the full implementation context; the language compiler, JVM, and standard library changes are intertwined. The separate pull requests exist only to subdivide the review and related discussion by area.

Any resulting code changes should be made in valhalla/lworld .

valhalla/lworld is currently updated from jdk/master whenever a weekly jdk tag is created. At that time, code changes from valhalla/lworld will be propagated to this pull request and to all sub-review pull requests.

Ultimately, review sign-off will be recorded on this " master pull request ", and the " sub-review pull requests " will be closed without integration.

This pull request has a large surface area and frequently conflicts with jdk/master . Refer to valhalla/lworld for the latest state of the project code, keeping in mind that it may lag several days behind jdk/master . Both repositories may be needed as references during review.

Checkout this PR locally: $ git fetch https://git.openjdk.org/jdk.git pull/31120/head:pull/31120 $ git checkout pull/31120

Update a local copy of the PR: $ git checkout pull/31120 $ git pull https://git.openjdk.org/jdk.git pull/31120/head

Checkout this PR locally: $ git pr checkout 31120

View PR using the GUI difftool: $ git pr show -t 31120

Download this PR as a diff file: https://git.openjdk.org/jdk/pull/31120.diff

Copy link Copy Markdown Member Author /issue add 8317277, 8317278, 8317279

Copy link Copy Markdown 👋 Welcome back dsimms! 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.

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Copy link Copy Markdown @MrSimms 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:

8389219: Implement JEP 401: Value Objects (Preview) 8389220: Implement JEP 539: Strict Field Initialization in the JVM (Preview) Co-authored-by: David Simms <dsimms@openjdk.org> Co-authored-by: Dan Smith <dlsmith@openjdk.org> Co-authored-by: Frederic Parain <fparain@openjdk.org> Co-authored-by: Tobias Hartmann <thartmann@openjdk.org> Co-authored-by: Roger Riggs <rriggs@openjdk.org> Co-authored-by: Vicente Romero <vromero@openjdk.org> Co-authored-by: Axel Boldt-Christmas <aboldtch@openjdk.org> Co-authored-by: Karen Kinnear <acorn@openjdk.org> Co-authored-by: Alex Menkov <amenkov@openjdk.org> Co-authored-by: Bill Huang <bhuang@openjdk.org> Co-authored-by: Benoît Maillard <bmaillard@openjdk.org> Co-authored-by: Christian Hagedorn <chagedorn@openjdk.org> Co-authored-by: Chris Plummer <cjplummer@openjdk.org> Co-authored-by: Casper Norrbin <cnorrbin@openjdk.org> Co-authored-by: Coleen Phillimore <coleenp@openjdk.org> Co-authored-by: David Beaumont <dbeaumont@openjdk.org> Co-authored-by: Daniel D. Daugherty <dcubed@openjdk.org> Co-authored-by: Damon Fenacci <dfenacci@openjdk.org> Co-authored-by: David Holmes <dholmes@openjdk.org> Co-authored-by: Dmitry Samersoff <dsamersoff@openjdk.org> Co-authored-by: Eric Caspole <ecaspole@openjdk.org> Co-authored-by: Evgeny Nikitin <enikitin@openjdk.org> Co-authored-by: Ekaterina Pavlova <epavlova@openjdk.org> Co-authored-by: Fei Yang <fyang@openjdk.org> Co-authored-by: Dan Heidinga <heidinga@openjdk.org> Co-authored-by: Harold Seigel <hseigel@openjdk.org> Co-authored-by: Ioi Lam <iklam@openjdk.org> Co-authored-by: Ivan Walulya <iwalulya@openjdk.org> Co-authored-by: Jatin Bhateja <jbhateja@openjdk.org> Co-authored-by: Jan Lahoda <jlahoda@openjdk.org> Co-authored-by: Jim Laskey <jlaskey@openjdk.org> Co-authored-by: John R Rose <jrose@openjdk.org> Co-authored-by: Joel Sikström <jsikstro@openjdk.org> Co-authored-by: Lois Foltan <lfoltan@openjdk.org> Co-authored-by: Chen Liang <liach@openjdk.org> Co-authored-by: Leonid Mesnik <lmesnik@openjdk.org> Co-authored-by: Matias Saavedra Silva <matsaave@openjdk.org> Co-authored-by: Marc Chevalier <mchevalier@openjdk.org> Co-authored-by: Mandy Chung <mchung@openjdk.org> Co-authored-by: Maurizio Cimadamore <mcimadamore@openjdk.org> Co-authored-by: Markus Grönlund <mgronlun@openjdk.org> Co-authored-by: Manuel Hässig <mhaessig@openjdk.org> Co-authored-by: Nick Gasson <ngasson@openjdk.org> Co-authored-by: Patricio Chilano Mateo <pchilanomate@openjdk.org> Co-authored-by: Paul Hübner <phubner@openjdk.org> Co-authored-by: Paul Sandoz <psandoz@openjdk.org> Co-authored-by: Quan Anh Mai <qamai@openjdk.org> Co-authored-by: Roberto Castañeda Lozano <rcastanedalo@openjdk.org> Co-authored-by: Roland Westrelin <roland@openjdk.org> Co-authored-by: Srikanth Adayapalam <sadayapalam@openjdk.org> Co-authored-by: Aleksey Shipilev <shade@openjdk.org> Co-authored-by: Stefan Johansson <sjohanss@openjdk.org> Co-authored-by: Sergey Kuksenko <skuksenko@openjdk.org> Co-authored-by: Serguei Spitsyn <sspitsyn@openjdk.org> Co-authored-by: Stefan Karlsson <stefank@openjdk.org> Co-authored-by: Thomas Stuefe <stuefe@openjdk.org> Co-authored-by: Thomas Schatzl <tschatzl@openjdk.org> Co-authored-by: Zoltan Majo <zmajo@openjdk.org> Co-authored-by: Alan Bateman <alanb@openjdk.org> Co-authored-by: Jaikiran Pai <jpai@openjdk.org> Co-authored-by: Martin Doerr <mdoerr@openjdk.org> Co-authored-by: Richard Reingruber <rrich@openjdk.org> Co-authored-by: Feilong Jiang <fjiang@openjdk.org> Co-authored-by: Daisuke Yamazaki <dyama@openjdk.org> Reviewed-by: mcimadamore, liach, darcy, dcubed, aboldtch, coleenp, iklam, jlahoda, dlong, jpai, vklang, heidinga, sspitsyn, cjplummer You can use pull request commands such as /summary , /contributor and /issue to adjust it as needed.

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MrSimms mentioned this pull request May 11, 2026 8317277: Java language implementation of value objects #31121 Closed 5 tasks openjdk Bot commented May 11, 2026 Copy link Copy Markdown @MrSimms 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 8317277 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 openjdk Bot commented May 11, 2026 Copy link Copy Markdown ⚠️ @MrSimms This pull request contains merges that bring in commits not present in the target repository. Since this is not a "merge style" pull request, these changes will be squashed when this pull request in integrated. If this is your intention, then please ignore this message. If you want to preserve the commit structure, you must change the title of this pull request to Merge <project>:<branch> where <project> is the name of another project in the OpenJDK organization (for example Merge jdk:master ).

openjdk Bot added csr Pull request needs approved CSR before integration merge-conflict Pull request has merge conflict with target branch labels May 11, 2026 openjdk Bot commented May 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page .

Copy link Copy Markdown @MrSimms This issue is referenced in the PR title - it will now be updated.

Adding additional issue to issue list: 8317278: JVM implementation of value classes and objects .

Adding additional issue to issue list: 8317279: Standard library implementation of value classes and objects .

This was referenced May 11, 2026 8317278: JVM implementation of value objects #31122 Closed 8317279: Standard library implementation of value objects #31123 Closed openjdk Bot added serviceability serviceability-dev@openjdk.org hotspot hotspot-dev@openjdk.org i18n i18n-dev@openjdk.org shenandoah shenandoah-dev@openjdk.org javadoc javadoc-dev@openjdk.org security security-dev@openjdk.org build build-dev@openjdk.org nio nio-dev@openjdk.org core-libs core-libs-dev@openjdk.org compiler compiler-dev@openjdk.org net net-dev@openjdk.org labels May 11, 2026 openjdk Bot commented May 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page .

Copy link Copy Markdown @MrSimms The following labels will be automatically applied to this pull request:

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

Dan Smith and others added 6 commits May 12, 2026 14:56 8383755: [lworld] Clean up Class.isValue and Class.isIdentity &hellip; 873f02d Reviewed-by: liach 8384050: [lworld] Update JDWP and JDI specs for JEP 401 &hellip; f39fa97 Reviewed-by: dholmes, sspitsyn 8384431: [lworld] Adjust tests affected by JDK-8370769 &hellip; e51da80 Reviewed-by: mchevalier 8384489: [lworld] ProblemList serviceability/jvmti/valhalla/SampledOb… &hellip; 2585704 …jectAllocValue/SampledObjectAllocValue.java Reviewed-by: fparain, cjplummer 8384487: [lworld] Fix minor typos in JDWP and JDI specs for JEP 401 &hellip; 96a8b4b Reviewe