Java 20: Key Features and Improvements

  • 30/3/2023
  • One-minute read

Java 20 (March 2023) is a short-term release. Most features ship as previews or incubators—ideal for experimentation, but not for production unless you plan to upgrade every six months.

Major Enhancements

  • Record Patterns (JEP 432, 2nd Preview): Deconstruct record classes directly in pattern matching.
  • Pattern Matching for switch (JEP 433, 4th Preview): Use type patterns and guarded patterns in switch expressions.
  • Virtual Threads (JEP 436, 2nd Preview): Lightweight threads built on Project Loom; test them for I/O-heavy services.
  • Scoped Values (JEP 429, Incubator): Share immutable context across threads without thread-local mutability.
  • Foreign Function & Memory API (JEP 434, 2nd Preview): Interoperate with native libraries without JNI.
  • Vector API (JEP 438, 5th Incubator): Leverage SIMD instructions via a stable abstraction.

Upgrade Checklist

  1. Test Preview Features: Enable with --enable-preview --release 20 when compiling and --enable-preview at runtime.
  2. Monitor Dependencies: Ensure frameworks (Spring, Quarkus, build tools) officially support Java 20.
  3. Experiment: Use staging environments to trial virtual threads or FFM; report feedback upstream.
  4. Plan for Java 21: Treat Java 20 as a stepping stone. Java 21 (LTS) will stabilise many of these features.

Resources

javaperformancejvmprogrammingvirtual-threads