[Jython-dev] JDK 21 Release Candidates & JVM Language Summit

[David D. <dav...@or...>]

Greetings!

JDK 21 is now in the Release Candidate Phase so everything is on track for the Java 21 GA release on September 19th! If you haven't done so, please start testing your project(s) using JDK 22 Early-Access builds and let us know the results.

In other news, the JVM Language Summit took place a few days ago in Santa Clara (California). During this unique gathering of Java architects and OpenJDK developers, key updates were shared and discussed, ex. where Valhalla stands today, the new Class-File API, an update on Leyden and Valhalla, Project Panama, the challenges of Virtual Threads, continuation internals, etc. We have started to publish the JVMLS 2023 videos so make sure to keep an eye on this evolving JVMLS playlist [1] to understand where the Java platform is heading to.


## JDK 21 Early-Access Builds

Per the JDK 21 schedule [2], we are now in the Release-Candidate Phase. The overall feature set [3] is frozen, no further JEPs will be targeted to this release.

### JEPs integrated to JDK 21:
- 430: String Templates (Preview)
- 431: Sequenced Collections
- 439: Generational ZGC
- 440: Record Patterns
- 441: Pattern Matching for switch  
- 442: Foreign Function & Memory API (3rd Preview)
- 443: Unnamed Patterns and Variables (Preview)   
- 444: Virtual Threads
- 445: Unnamed Classes and Instance Main Methods (Preview)
- 446: Scoped Values (Preview)
- 448: Vector API (6th Incubator)
- 449: Deprecate the Windows 32-bit x86 Port for Removal
- 451: Prepare to Disallow the Dynamic Loading of Agents
- 452: Key Encapsulation Mechanism API
- 453: Structured Concurrency (Preview)

The first JDK 21 Release Candidate builds (builds 35) are available [4]. Those builds are provided under the GNU General Public License v2, with the Classpath Exception. The Release Notes [5] and the Javadocs [6] are also available.

[1] https://www.youtube.com/playlist?list=PLX8CzqL3ArzW90jKUCf4H6xCKpStxsOzp
[2] https://openjdk.org/projects/jdk/21/#Schedule
[3] https://openjdk.org/projects/jdk/21/#Features
[4] https://jdk.java.net/21/
[5] https://jdk.java.net/21/release-notes
[6] https://download.java.net/java/early_access/jdk21/docs/api/


## JDK 22 Early-Access Builds

The latest Early-Access builds 11 are available [7], and are provided under the GNU General Public License v2, with the Classpath Exception. The Release Notes are available here [8].

### Changes in recent JDK 22 builds (b8-b11) that may be of interest:

Note that this is only a curated list of changes, make sure to check [9] for additional changes.

- JDK-8314209: Wrong @since tag for RandomGenerator::equiDoubles [Reported by JaCoCo]
- JDK-8312489: Increase Default Value of the System Property jdk.jar.maxSignatureFileSize
- JDK-8312433: HttpClient request fails due to connection being considered …
- JDK-8313307: java/util/Formatter/Padding.java fails on some Locales
- JDK-8312821: Javac accepts char literal as template
- JDK-8313251: Add NativeLibraryLoad event
- JDK-8313809: String template fails with java.lang.StringIndexOutOfBoundsE…
- JDK-8312984: javac may crash on a record pattern with too few components
- JDK-8310033: Clarify return value of Java Time compareTo methods
- JDK-8302017: Allocate BadPaddingException only if it will be thrown
- JDK-8310913: Move ReferencedKeyMap to jdk.internal so it may be shared
- JDK-8313251: Add NativeLibraryLoad event to provide more detail about shared lib/dll loads
- JDK-8311653: Modify -XshowSettings launcher behavior
- JDK-8306441: Two phase segmented heap dump
- JDK-8311981: JVM May Hang When Using Generational ZGC if a VM Handshake Stalls on Memory
- JDK-8308850: Change JVM options with small ranges that get -Wconversion warnings to 32 bits

[7] https://jdk.java.net/22/
[8] https://jdk.java.net/22/release-notes
[9] https://github.com/openjdk/jdk/compare/jdk-22%2B8...jdk-22%2B11


## JavaFX 21 & 22 Early-Access Builds

These are early-access builds of the JavaFX Runtime, built from openjdk/jfx [10]. They allow JavaFX application developers to build and test their applications with JavaFX 21 or 22 on the latest JDK.

The latest builds 29 (2023/8/7) of JavaFX 21 are now available [11]. The early-access builds 5 (2023/8/18) of the JavaFX 22 Runtime which is designed to work with JDK 22 are also available [12]. These early-access builds are provided under the GNU General Public License, version 2, with the Classpath Exception. Please send the feedback on the openjfx-dev mailing list [13].

[10] https://github.com/openjdk/jfx
[11] https://jdk.java.net/javafx21/
[12] https://jdk.java.net/javafx22/
[13] http://mail.openjdk.org/mailman/listinfo/openjfx-dev


## Topics of Interest:

JDK 21: G1/Parallel/Serial GC improvements
https://tschatzl.github.io/2023/08/04/jdk21-g1-parallel-gc-changes.html

To Java 21 and Beyond!
https://inside.java/2023/08/08/to-java21-and-beyond/

Strengthen your Java App's Defenses with Key Encapsulation Mechanism API
https://inside.java/2023/08/03/newscast-54/

JVMLS - Foreign Function & Memory API
https://inside.java/2023/08/21/jvmls-ffm-api/

JVMLS - Java and GPU … are we nearly there yet?
https://inside.java/2023/08/22/java-and-gpu/

Draft JEP: Computed Constants
https://minborgsjavapot.blogspot.com/2023/08/java-new-draft-jep-computed-constants.html

Using Computed Constants to Manage Static State in Leyden
https://cr.openjdk.org/~jrose/leyden/after-computed-constants.html

Project Leyden: Toward Condensers
https://openjdk.org/projects/leyden/notes/03-toward-condensers

New OpenJDK Container mailing list
https://mail.openjdk.org/pipermail/container-discuss/2023-August/000000.html

Introduction: Q-descriptors and v-bytecodes
https://cr.openjdk.org/~jrose/values/larval-values.html

~

Until next time!

--David