Java Version 20 Peek at the Future

Java 20, released in March 2023, continues the Java platform’s steady evolution. Like Java 18 and 19, this is a non-LTS (non-Long-Term Support) release and is primarily composed of preview and incubator features.

If you’ve been tracking Projects Loom, Amber, and Panama, Java 20 delivers critical updates to each.

While no major language features are finalized in this release, Java 20 is a developer’s playground—a forward-looking toolkit that sets the stage for significant LTS changes in Java 21.

Let’s dive into the key enhancements and new capabilities in Java 20.

1. Scoped Values (Incubator) — JEP 429

Scoped Values are a new way to share immutable data across threads—especially virtual threads—without the need for thread-local variables, which can be inefficient and error-prone in high-concurrency environments.

Why it matters:

• Safer and faster alternative to ThreadLocal

• Immutable, thread-constrained data sharing

• Plays nicely with structured concurrency

For example:

ScopedValue<String> USER_ID = ScopedValue.newInstance();

ScopedValue.where(USER_ID, "alice").run(() -> {

System.out.println(USER_ID.get()); // prints "alice"

});

2. Record Patterns (Second Preview) — JEP 432

Building on the first preview from Java 19, this update refines record pattern matching by improving exhaustiveness checking and pattern composition.

Recap: Record patterns allow you to deconstruct data more concisely.

For example:

record Point(int x, int y) {}

void print(Object o) {

if (o instanceof Point(int x, int y)) {

System.out.println("X = " + x + ", Y = " + y);

}

}

3. Pattern Matching for Switch (Third Preview) — JEP 433

Java 20 brings more polish and enhancements to the pattern matching for switch, including:

• Simpler syntax rules

• Better exhaustiveness checks

• Improved handling of null

This feature continues to evolve toward finalization, expected in a future LTS release.

4. Virtual Threads (Second Preview) — JEP 436

Introduced in Java 19, Virtual Threads get important updates and bug fixes in their second preview. These threads are a cornerstone of Project Loom, dramatically improving Java's concurrency model.

Recap:

• Lightweight threads managed by the JVM

• Millions of virtual threads with minimal resources

• Great for web servers and async tasks

For example:

Thread.startVirtualThread(() -> {

System.out.println("Hello from a virtual thread!");

});

5. Structured Concurrency (Second Incubator) — JEP 437

Java 20’s incubator version of Structured Concurrency refines the API to better manage groups of related concurrent tasks. It's a cleaner, more maintainable way to coordinate multithreaded work.

For example:

try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {

Future<String> profile = scope.fork(() -> getUserProfile());

Future<String> avatar = scope.fork(() -> getUserAvatar());

scope.join(); // Waits for both

scope.throwIfFailed(); // Fails fast if any fail

return profile.result() + avatar.result();

}

6. Foreign Function & Memory API (Third Preview) — JEP 434

Part of Project Panama, this preview includes refinements to the Foreign Function and Memory (FFM) API introduced in earlier releases.

Use Cases:

• Calling native code (like C libraries)

• Working with off-heap memory

• Replacing JNI in a safer and more idiomatic way

For example:

Linker linker = Linker.nativeLinker();

SymbolLookup lookup = SymbolLookup.systemLookup();

MemorySegment strlen = lookup.find("strlen").get();

Summary Table

Feature	JEP	Status	Origin Project
Scoped Values	429	Incubator	Project Loom
Record Patterns (2nd Preview)	432	Preview	Project Amber
Pattern Matching for Switch (3rd)	433	Preview	Project Amber
Virtual Threads (2nd Preview)	436	Preview	Project Loom
Structured Concurrency (2nd)	437	Incubator	Project Loom
Foreign Function & Memory (3rd)	434	Preview	Project Panama

Should You Upgrade?

✅ Upgrade if you’re:

• Exploring virtual threads and structured concurrency for high-throughput applications

• Interested in replacing JNI with the Foreign Function & Memory API

• Experimenting with pattern matching and deconstruction for cleaner code

⏳ Hold off if you’re:

• Running Java 17 in production and waiting for the LTS release (Java 21)

• Not using preview or incubator features in your codebase

Final Thoughts

Java 20 doesn't add final features to the language or JVM, but it’s a powerful platform for experimentation. If you're building the next generation of high-performance Java apps or planning for Java 21, now is the time to try these capabilities.