Primitive Types in Patterns, instanceof, and switch (Preview)
Patterns, instanceof, and switch can mention primitive types. This is a preview.
Second preview in Java 24 (JEP 488). Third preview in Java 25 (JEP 507). It is not final in Java 25.
JDK 23 · JSR 398
Java 23
JDK 23 is Java SE 23, JSR 398, generally available on 17 September 2024. Markdown documentation comments become standard. Primitive patterns, module import declarations, and flexible constructor bodies are previews. ZGC uses the generational mode by default. Stream gatherers and the class-file API are still previews.
How to read the status
- Final. The change shipped in this release as a permanent part of that release.
- Preview. It can be tried with --enable-preview. A preview is not a permanent language or API guarantee.
- Incubator. An incubator API is not a supported standard API. It can change or be removed.
Language
Module Import Declarations (Preview)
import module M is a preview. It imports the public types of the packages a module exports.
Final in Java 25 (JEP 511).
Flexible Constructor Bodies (Second Preview)
Statements before super(...) are previewed again.
First preview in Java 22 (JEP 447). Final in Java 25 (JEP 513).
Implicitly Declared Classes and Instance Main Methods (Third Preview)
The compact-program preview continues.
Final in Java 25 as compact source files (JEP 512).
APIs / Libraries
Stream Gatherers (Second Preview)
Stream gatherers are previewed a second time.
Final in Java 24 (JEP 485).
OpenJDK JEP 473 (leaves JavaMastery)
Related reading: Streams and Optional
Class-File API (Second Preview)
The class-file API is previewed a second time.
Final in Java 24 (JEP 484).
Structured Concurrency (Third Preview)
Structured concurrency is previewed a third time.
Still a preview in Java 25.
OpenJDK JEP 480 (leaves JavaMastery)
Related reading: Concurrency
Scoped Values (Third Preview)
Scoped values are previewed a third time.
Final in Java 25 (JEP 506).
OpenJDK JEP 481 (leaves JavaMastery)
Related reading: Concurrency
Deprecate the Memory-Access Methods in sun.misc.Unsafe for Removal
The memory-access methods of sun.misc.Unsafe are deprecated for removal. They are not removed in this release.
Vector API (Eighth Incubator)
The Vector API incubates an eighth time.
Still incubating in Java 25.
JVM / Runtime
ZGC: Generational Mode by Default
ZGC’s default mode is generational. Non-generational ZGC is still available in this release.
Generational ZGC arrived in Java 21 (JEP 439). Java 24 removes the non-generational mode (JEP 490).
OpenJDK JEP 474 (leaves JavaMastery)
Related reading: JVM and memory
Tools / Platform
Markdown Documentation Comments
Documentation comments can be written in Markdown as well as in the traditional comment syntax.
Related reading
Historical notes
String templates are not in this release. Their last preview in this curriculum is Java 22. There is no Java 23 sample. The language changes here were previews. Later final forms are the Java 24 gatherers example and the Java 25 module-import and constructor examples.
Sources. General availability, JSR 398, and the JEP list: OpenJDK JDK 23. OpenJDK JDK 23 (leaves JavaMastery)