[Jython-dev] JDK 20 Rampdown Phase 1 & Valhalla LW4 Early-Access builds

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Welcome to the final OpenJDK Quality Outreach update for 2022!

JDK 20, scheduled for General Availability on March 21 2023, is now in 
Rampdown Phase One (RDP1) [1]. At this point, the overall JDK 20 [2] 
feature set is frozen (see below the final list of JEPs integrated into 
JDK 20) and only low-risk enhancements might still be considered. The 
coming weeks should be used to identify and resolve as many issues as 
possible, i.e. before JDK 20 enters the Release Candidates phase in 
early February 2023.

## JDK 20 Early-Access builds

The latest Early-Access (builds 27) are available [2] with the Release 
Notes here [3]. Those builds are provided under the GNU GPL v2, with the 
Classpath Exception.

### JEPs integrated into JDK 20:

- JEP 429: Scoped Values (Incubator)
- JEP 432: Record Patterns (2nd Preview)
- JEP 433: Pattern Matching for switch (4th Preview)
- JEP 434: Foreign Function & Memory API (2nd Preview)
- JEP 436: Virtual Threads (2nd Preview)
- JEP 437: Structured Concurrency (2nd Incubator)

[1] https://mail.openjdk.org/pipermail/jdk-dev/2022-December/007233.html
[2] https://jdk.java.net/20/
[3] https://jdk.java.net/20/release-notes

### Changes in recent JDK 20 builds that may be of interest:

#### Build 27:
- JDK-8297794: Deprecate JMX Management Applets for Removal
- JDK-8297118: Change IncompatibleClassChangeError to MatchException for 
exhaustive switch statements and switch expressions
- JDK-8294047: HttpResponseInputStream swallows interrupts
- JDK-8281236: (D)TLS key exchange named groups
- JDK-8280798: com.sun.jdi.ObjectReference::setValue spec should 
prohibit any final field modification
- JDK-8295350: JFR: Add stop methods for recording streams
- JDK-8295044: Implementation of Foreign Function and Memory API (2nd 
Preview)
- JDK-8296896: Change virtual Thread.yield to use external submit
- JDK-8297804: (tz) Update Timezone Data to 2022g
- JDK-8295803: Console should be usable in jshell and other environments
- JDK-8286666: Implementation of Scoped Values (Incubator)
- JDK-8296672: Implementation of Virtual Threads (2nd Preview)

#### Build 26:
- JDK-8297276: Remove thread text from Subject.current
- JDK-8297030: Reduce Default Keep-Alive Timeout Value for httpclient
- JDK-8247645: ChaCha20 Intrinsics

#### Build 25:
- JDK-8296472: Remove ObjectLocker around 
appendToClassPathForInstrumentation call
- JDK-8290313: Produce warning when user specified java.io.tmpdir 
directory doesn't exist
- JDK-8288717: Add a means to close idle connections in HTTP/2 
connection pool
- JDK-8288047: Accelerate Poly1305 on x86_64 using AVX512 instructions
- JDK-8059632: Method reference compilation uses incorrect qualifying type
- JDK-8297161: Add additional Service Attributes to Standard Algorithm 
Names guide
- JDK-8294073: Performance improvement for message digest implementations

#### Build 24:
- JDK-8294731: Improve multiplicative inverse for secp256r1 implementation
- JDK-8296715: CLDR v42 update for tzdata 2022f
- JDK-8296958: [JVMCI] add API for retrieving ConstantValue attributes

#### Build 23:
- JDK-8296226: Add constructors (String,Throwable) and (Throwable) to 
InvalidParameterException
- JDK-8295673: Deprecate and disable legacy parallel class loading 
workaround for non-parallel-capable class loaders
- JDK-8294241: Deprecate URL public constructors
- JDK-8289689: (fs) Re-examine the need for normalization to Unicode 
Normalization Format D (macOS)
- JDK-8279164: Disable TLS_ECDH_* cipher suites
- JDK-8178355: IdentityHashMap uses identity-based comparison for values 
everywhere except remove(K,V) and replace(K,V,V)
- JDK-8296108: (tz) Update Timezone Data to 2022f

## Heads-up - JDK 21: First Early-Access Builds

When JDK 20 entered RDP1 [4], the JDK mainline [5] was (a) forked into a 
JDK 20 stabilization repository [6], and (b) set to JDK 21. As a 
consequence, the first JDK 21 Early-Access builds have been published [7].

[4] https://mail.openjdk.org/pipermail/jdk-dev/2022-December/007233.html
[5] https://github.com/openjdk/jdk
[6] https://github.com/openjdk/jdk20
[7] https://jdk.java.net/21/

## Heads-up - Valhalla: LW4 Early-Access Builds

Valhalla LW4 early-access builds have been published [8], those builds 
are primarily focused on implementing the Value Objects JEP draft [9]. 
For additional details on those EA builds, make sure to read these LW4 
release notes [10]. For a more hands-on introduction to Value Object, 
you can watch the latest JEP Café: Java Value Objects in Action [11]. 
Interested developers are encouraged to explore the performance and 
migration impact of value objects on their applications, and to provide 
feedback to the valhalla-dev [12] mailing list.

[8] https://jdk.java.net/valhalla/
[9] https://openjdk.org/jeps/8277163
[10] https://openjdk.org/projects/valhalla/early-access
[11] https://inside.java/2022/12/06/jepcafe15/
[12] https://mail.openjdk.org/pipermail/valhalla-dev/

## Heads-up - Generational ZGC: New Early-Access Builds

New Generational ZGC [13] Early-Access Builds have been updated recently 
[14]. These EA builds are provided under the GNU GPL v2, with the 
Classpath Exception.

### Changes include :
- Rebased on top of jdk-20+21
- Added macOS builds
- Heuristics rewriten to deal with a problematic case where Generational 
ZGC spent too much focus on doing young generation collection when it’s 
more beneficial to spend resources to collect the old generation.
- GC logging rewriten to easier see what log lines belong to what 
collection / generation, plus many additional changes that should make 
it easier to read and understand GC logs
- Barrier elision enhanced to remove barriers from array access of newly 
allocated arrays
- Enhanced the generated hs_err crash text file
- Fixed and unified code quality and style

For more information, make sure to watch this Inside Java Newscast [15] 
dedicated on Generational ZGC. Feedback should be sent to the zgc-dev 
mailing list [16].

[13] https://jdk.java.net/genzgc/
[14] https://bugs.openjdk.org/browse/JDK-8272979
[15] https://inside.java/2022/11/17/insidejava-newscast-037/
[16] https://mail.openjdk.org/pipermail/zgc-dev/

## JavaFX 20 Early-Access Builds

These are early access builds of the JavaFX 20 Runtime, built from 
openjdk/jfx [17]. They allow JavaFX application developers to build and 
test their applications with JavaFX 20 on JDK 20. The latest builds 10 
(2022/12/5) are now available [18] with javadoc here [19]. Feedback 
should be forwarded to the openjfx-dev [19] mailing list. For more 
details, you might want to listen this Inside Java podcast episode [20].

[17] https://github.com/openjdk/jfx
[18] https://jdk.java.net/javafx20/
[19] 
https://download.java.net/java/early_access/javafx20/docs/api/overview-summary.html
[20] http://mail.openjdk.org/mailman/listinfo/openjfx-dev
[21] https://inside.java/2022/11/18/podcast-027/

## Topics of Interest:

- Building and Deploying Java Client Desktop Applications with JDK 17 
and Beyond
https://inside.java/2022/12/08/building-java-desktop-app/

- Java Value Objects in Action with Valhalla - JEP Café #15
https://inside.java/2022/12/06/jepcafe15/

- Java 20 - Sneak Peek on the Foreign Function & Memory API
https://minborgsjavapot.blogspot.com/2022/12/java-20-sneak-peek-on-panama-ffm-api.html

- A Glimpse at Java 20 - Pattern Matching, Concurrent Programming and 
Valhalla - Inside Java Newscast #38
https://inside.java/2022/12/01/newscast-38/

- “JavaFX” - Inside Java Podcast #27
https://inside.java/2022/11/18/podcast-027/

- Generational ZGC - Inside Java Newscast #37
https://inside.java/2022/11/17/insidejava-newscast-037/

- Java 17 to 20 Pattern Matching full tutorial with Records, Instanceof 
and Switch - JEP Café #14
https://inside.java/2022/11/08/jepcafe14/

- Script Friendly JDK Download URLs
https://inside.java/2022/11/14/sip072/

- Using the JShell API to improvement a Java Source Browser
https://inside.java/2022/11/21/jshell-java-source-browser/

~

As usual, let us know if you find any quirks while testing your 
project(s) on the latest JDK early-access builds. As year-end is 
approaching, I'd like to thank you for being part of the OpenJDK Quality 
Outreach Program. I hope that you will disconnect a bit to spend time 
with your family and your friends. See you in 2023 with Java 20 and Java 21!

--David