Java 19 Previews the Future

Java 19, released in September 2022, continues the OpenJDK six-month release cadence and serves as a non-LTS feature release, much like Java 18.

While it doesn’t introduce sweeping changes for everyday enterprise applications, Java 19 brings an exciting mix of preview and incubator features that give us a sneak peek into the future of Java—particularly in areas like virtual threads, structured concurrency, and foreign function interoperability.

Let’s explore what’s inside Java 19 and how it sets the stage for massive improvements in performance, concurrency, and native code integration.

1. Virtual Threads (Preview) — JEP 425

Virtual threads are lightweight, user-mode threads managed by the Java Virtual Machine rather than the OS. They are part of Project Loom, which aims to dramatically simplify concurrent programming.

Why it matters:

• Create millions of threads with minimal overhead.

• Ideal for high-throughput server applications (e.g., web services).

• Dramatically reduces boilerplate from ExecutorService patterns.

For example:

try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {

IntStream.range(0, 1000).forEach(i ->

executor.submit(() -> System.out.println("Thread " + i))

);

}

2. Structured Concurrency (Incubator) — JEP 428

Also part of Project Loom, Structured Concurrency provides a cleaner and more reliable way to manage multiple concurrent tasks as a single unit of work—making your code easier to reason about, test, and debug.

For example:

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

Future<String> user = scope.fork(() -> fetchUser());

Future<String> order = scope.fork(() -> fetchOrder());

scope.join(); // Wait for all subtasks

scope.throwIfFailed(); // Propagate exceptions

return user.result() + order.result();

}

3. Pattern Matching for Switch (Second Preview) — JEP 427

Refining what began in Java 17 and expanded in 18, Java 19 includes the second preview of Pattern Matching for Switch, part of Project Amber.

Enhancements:

• Guarded patterns (case String s when s.length() > 5)

• Exhaustiveness checking

• Better support for nulls

For example:

static String describe(Object obj) {

return switch (obj) {

case Integer i -> "Integer " + i;

case String s when s.length() > 5 -> "Long string";

case String s -> "Short string";

case null -> "Null!";

default -> "Unknown";

};

}

4. Record Patterns (Preview) — JEP 405

Record Patterns allow deconstruction of record values directly in instanceof checks and switch cases, enabling much more expressive and declarative code.

For example:

record Point(int x, int y) {}

void process(Object obj) {

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

System.out.println("Point at (" + x + ", " + y + ")");

}

}

5. Foreign Function & Memory API (Preview) — JEP 424

This is the rebranded and refined version of the earlier Panama efforts (JEP 412, 419). It provides a modern API for calling native code (like C libraries) without JNI, and for working with off-heap memory safely and efficiently.

Use Case:

• Calling native C libraries (e.g., OpenSSL, zlib)

• Working with memory outside the Java heap

For example:

try (Arena arena = Arena.ofConfined()) {

MemorySegment segment = arena.allocate(100);

// Use segment for native calls

}

Benefits:

• Safer than JNI

• More performant

• Easier to maintain

6. Vector API (Fourth Incubator) — JEP 426

This version of the Vector API improves support for hardware SIMD (Single Instruction, Multiple Data) operations—enabling faster data processing by operating on multiple data points simultaneously.

Improvements in this version:

• Improved performance portability

• Expanded set of operations

• Better compiler optimizations

Example Use Case:

• Processing arrays for machine learning, image processing, cryptography

Final Thoughts

Java 19 doesn’t include any final language features or major syntax changes, but it builds powerful foundations for future releases. Developers who explore these incubating and preview features today will be better prepared when they become standard tomorrow.

Should You Upgrade?

✅ Upgrade if you’re:

• Exploring Project Loom (virtual threads, structured concurrency)

• Working with native code (FFM API)

• Prototyping libraries or high-performance systems

⏳ Hold off if you’re:

• In production with Java 17 and don’t need bleeding-edge concurrency

• Waiting for preview features to stabilize in LTS releases (e.g., Java 21)

What’s Coming Next?

Looking ahead, many of these features (virtual threads, structured concurrency, record patterns) are expected to mature in Java 20 and be finalized in Java 21, the next LTS version. That means Java 19 is a great sandbox to start preparing your applications for the future.