Thread by @nipafx

#Java18 comes out later today - what can you expect from Java's newest release? Here's a 🧵 with one tweet per feature - short and sweet.

For more details and links, read this blog post: nipafx.dev/inside-java-ne…
For questions, join our #JDK18 AMA later today. 👇🏾

https://twitter.com/BillyKorando/status/1505597399275876359

Pattern Matching for `switch` (2nd preview)
openjdk.java.net/jeps/420

Changes:
* constant case labels must now appear before guarded patterns of the same type
* exhaustiveness checking is now more precise when sealed classes and generics mix

Another preview is expected in #JDK19.

Vector API (3rd incubation)
openjdk.java.net/jeps/417

Changes:
* support for ARM Scalar Vector Extension (SVE)
* performance for masked ops improved on architectures that support masking in hardware

Vector API will stay incubating until Valhalla's value/primitive types.

Foreign Function & Memory API (2nd incubator)
openjdk.java.net/jeps/419

Changes:
* more carriers
* obtaining downcall method handles is simpler
* managing temporal dep's between resource scopes is simpler
* more general dereference API
* new API to copy Java arrays to/from memory

Simple Web Server
openjdk.java.net/jeps/408


Start a web server that hosts files in a directory for tests/demos/experiments with `jwebserver`. It's super simple on purpose: only HEAD and GET, no support for authentication, access control, encryption, etc.

Internet-Address Resolution SPI
openjdk.java.net/jeps/418

A service-provider interface for host name and IP resolution, so `java​.net.InetAddress` doesn't have to rely on `hosts` file or pin threads (#ProjectLoom).

More in the next Newscast - subscribe: youtube.com/java

Deprecating Finalization for Removal
openjdk.java.net/jeps/421


Due to various flaws (unpredictable timing & threading, error-prone, security implications) finalization is deprecated for removal. To preview removal, test with `java --finalization=disabled`.

UTF-8 by Default
openjdk.java.net/jeps/400
inside.java/2021/10/04/the…

If no file encoding is specified, file APIs now use UTF-8 instead of determining a fallback from OS/user settings. Stick to old behavior with `-Dfile.encoding=COMPAT`, prepare with `-Dfile.encoding=UTF-8`.

Reflection via Method Handles
openjdk.java.net/jeps/416

The JDK had three mechanisms for reflective ops:

1. VM native methods
2. bytecode stubs and Unsafe
3. method handles

Code using 2. was refactored to 3. and 2. was removed, so future lang additions require less work.

Javadoc Code Snippets
openjdk.java.net/jeps/413


Instead of writing demo code as text in Javadoc (which is agonizing and brittle), place it in a compiled and tested source file and then reference that or a section of it from Javadoc.

There are very few smaller API additions in #JDK18. The most noteworthy are in `Math` and `StrictMath`, which gained methods that combine division and modulo computations with rounding, for example to compute the result of 4 divided by 3, rounded up.

As always, there are plenty of security fixes (keep an eye out for @seanjmullan's post on seanjmullan.org/blog/) and performance improvements (also in the next Inside Java Newscast on youtube.com/java).

Now I'm curious to learn: What's the newest JDK version you'll be using in production in the next weeks. (Twitter polls only allow four choices, so please forgive me if you're in between or below 8. 😊)

🤔