asmhatreandClaude Sonnet 5
f59c1de96d
Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3
javademos
Runnable companion code for the ankurm.com post "Java 27 Is Out: Every JEP, Plus the Java 26 Changes You Skipped", and for the Java version guides
(https://ankurm.com/java-21-to-25-lts-features/). Every number and transcript in the post comes from a file in docs/output/, produced by a script in scripts/.
What was tested against
| Thing | Version | Note |
|---|---|---|
| JDK 21 (LTS) | Amazon Corretto 21.0.12.1 | the start of the 21 to 25 lane |
| JDK 25 (LTS) | Temurin 25.0.4.1+1 | the baseline for "broke on 26" |
| JDK 26 | Amazon Corretto 26.0.2.1 | GA 2026-03-17, non-LTS |
| JDK 27 | Amazon Corretto 27+35 | GA 2026-09-15, non-LTS |
| Containers | amazoncorretto:23, :24 (when did it change?), :26, :27 |
same vendor for both, so only the JDK version changes |
| JOL | 0.17 | downloaded and sha1-checked by scripts/object-headers.sh |
Next LTS: Java 29, September 2027 (Oracle Java SE Support Roadmap). Layout: g1-container/, object-headers/, jep-tour/ (27 features and broken/ 26-era sources),
recap26/ (the Java 26 lane), lanes/ (the 21 to 25 hub demos, the AI prompts in lanes/prompts/ and the build-file demo in lanes/upgrade/), other-changes/, api-diff/.
Quickstart
export JDK21=/path/to/jdk-21 JDK25=/path/to/jdk-25 JDK26=/path/to/jdk-26 JDK27=/path/to/jdk-27 # defaults are in scripts/env.sh
./scripts/jep-tour.sh # the five 27 feature demos, self-asserting
./scripts/recap26.sh # the 26 recap lane
./scripts/lanes.sh # the 21 to 25 hub claims, checked on 21, 23, 24, 25, 26, 27
./scripts/upgrade.sh # the build-file half: Maven, Gradle, Lombok, --release, jdeps (needs Maven Central)
./scripts/run-all.sh # regenerate every docs/output/*.txt (about 15-20 minutes; needs Docker)
Timings, RSS, GC counts and the Vector species are machine dependent; treat them as shape, not results. Everything else is byte-stable.
Chapters
Captured output (docs/output/)
| File | Produced by | What it is |
|---|---|---|
01-03 |
g1-default.sh |
which collector each JDK picks, by container size; the opt-out |
04-06 |
g1-cost.sh, g1-tuning.sh |
what G1 costs on one CPU, and two tested explanations |
10-15 |
object-headers.sh |
JOL instance sizes on 26, 27, 27 opted out; the JOL record failure and workaround |
20-broken-* |
broken-on-27.sh |
javac's own messages for 26-era preview code on 27 |
21-25 |
jep-tour.sh |
the five 27 feature demos |
30-32 |
tls-pq.sh |
key-exchange matrix, ClientHello size, the opt-out |
40 |
jfr-redaction.sh |
five redaction configurations |
50-52 |
api-diff.sh |
public API diffs, 26 to 27, 25 to 26, Vector only |
60-62 |
other-changes.sh |
removed options, behaviour changes, new 27 API |
70-75 |
recap26.sh |
final-field mutation, AOT cache matrix and startup, removals, 26 API, HTTP/3 |
92-97 |
upgrade.sh |
Maven release 25 on JDK 21, 25, 27, Gradle 8 vs 9 on JDK 25, --release vs -source/-target, Lombok and Mockito by version, jdeps --jdk-internals |
80-91 |
lanes.sh |
the 21 to 25 hub claims on JDK 21, 23, 24, 25, 26, 27: scoped values, structured concurrency, finalization, pinning, ZGC flags, warnings |
Not reproduced
jdk.java.net/27 and openjdk.org/jeps returned 403 while this was written; the JEP list was cross-checked against four secondary sources and the JDK binaries themselves.
HTTP/3 was not spoken to a real HTTP/3 server (no UDP egress). JEP 522 was not benchmarked. JDK-8377013 could not be reproduced.
MIT licensed, see LICENSE.