DEV Community

araf
araf

Posted on

What's New in JDK 24: Final, Preview, Incubator & Experimental Features with Real Examples

#programming #java #coding #development

Java Development Kit (JDK) 24, released in March 2025, delivers significant enhancements in language design, performance, runtime, and developer productivity. This guide covers the new features by category — Final, Preview, Incubator, and Experimental — with examples and practical use cases.

✅ Final Features

🔹 JEP 457: Class-File API

Standard API for reading, writing, and transforming .class files. Great for IDEs, agents, and static analyzers.

ClassModel model = ClassFile.read(Path.of("MyClass.class"));
model.methods().forEach(System.out::println);
Enter fullscreen mode Exit fullscreen mode

🔹 JEP 461: Stream Gatherers

A flexible abstraction to define custom stream collection logic.

var result = List.of("Java", "24", "rocks")
    .stream()
    .collect(Gatherers.joining(" "));
System.out.println(result); // Java 24 rocks
Enter fullscreen mode Exit fullscreen mode

🧪 Preview Features (Use --enable-preview)

🧩 JEP 488: Primitive Types in Patterns, instanceof, and switch (Second Preview)

Pattern matching now supports primitive types in all contexts (instanceof, switch, record patterns).

Object input = 42;
if (input instanceof int i) {
    System.out.println("It's an int: " + i);
}
Enter fullscreen mode Exit fullscreen mode

🧩 JEP 494: Module Import Declarations (Second Preview)

Allows succinct import of entire modules, streamlining modular code reuse.

import module java.se.*; // Hypothetical syntax
Enter fullscreen mode Exit fullscreen mode

🧩 JEP 492: Flexible Constructor Bodies (Third Preview)

Supports statements before super(...) or this(...) in constructors, enabling early field initialization.

class User {
    final String id;
    User(String name) {
        id = name.toUpperCase(); // Allowed before super()
        super();
    }
}
Enter fullscreen mode Exit fullscreen mode

🧩 JEP 495: Simple Source Files and Instance Main Methods (Fourth Preview)

Allows writing programs without needing a class declaration.

void main() {
    System.out.println("Hello from simple Java!");
}
Enter fullscreen mode Exit fullscreen mode

🧩 JEP 487: Scoped Values (Fourth Preview)

Share immutable context across threads more safely than ThreadLocal.

ScopedValue<String> USER_ID = ScopedValue.newInstance();
ScopedValue.runWhere(USER_ID, "abc123", () -> {
    System.out.println(USER_ID.get());
});
Enter fullscreen mode Exit fullscreen mode

🧩 JEP 478: Key Derivation Function API

New cryptographic API for deriving secure keys.

KDF kdf = KDF.getInstance("HKDF");
SecretKey derived = kdf.deriveKey(...);
Enter fullscreen mode Exit fullscreen mode

🚧 Incubator Features

🔬 JEP 489: Vector API (Ninth Incubator)

Offers SIMD-style programming with reliable runtime compilation to vector instructions.

FloatVector va = FloatVector.fromArray(SPECIES, a, 0);
FloatVector vb = FloatVector.fromArray(SPECIES, b, 0);
FloatVector vc = va.add(vb);
Enter fullscreen mode Exit fullscreen mode

🧬 Experimental Features

🧪 JEP 450: Compact Object Headers

Reduces memory footprint and increases performance via smaller object headers. Enabled with:

-XX:+UnlockExperimentalVMOptions -XX:+UseCompactObjectHeaders
Enter fullscreen mode Exit fullscreen mode

🧪 JEP 483: Ahead-of-Time Class Loading and Linking

Improves startup time by preloading class metadata during previous runs.

🧪 JEP 491: Synchronize Virtual Threads without Pinning

Enhances virtual thread scalability by avoiding platform thread pinning.

🔧 Additional Improvements

  • JEP 499: Structured Concurrency (Fourth Preview) – Treat related threads as a single unit for better cancellation and error handling.
  • JEP 475: Late Barrier Expansion for G1 – Performance boost for the G1 garbage collector.
  • JEP 490: ZGC now runs in generational mode by default.
  • JEP 486: Security Manager permanently disabled.
  • JEP 496/497: Quantum-resistant cryptographic algorithms.

💡 Real-World Use Cases

Use Case Feature Why It’s Useful
Bytecode tools Class-File API Easy .class parsing/modification
Stream processing Stream Gatherers Custom intermediate operations
Cryptographic systems KDF API, Quantum-safe Modern, secure cryptography
Teaching & scripting Simple Source Files Beginner-friendly Java
Thread context Scoped Values Safe data sharing across threads

🛠️ Get Started with JDK 24

  1. Download: OpenJDK 24 or Oracle JDK 24
  2. Compile Preview Code: 
javac --enable-preview --release 24 Example.java
java --enable-preview Example
Enter fullscreen mode Exit fullscreen mode
  1. Use a Supported IDE: IntelliJ IDEA, Eclipse, or VS Code with Java 24 plugin.

🚀 Wrap-up

JDK 24 continues Java’s mission to evolve for modern applications. From better startup and memory usage to developer ergonomics and secure cryptography — it’s a strong upgrade for devs at any level.

👉 Have you tried Java 24? What’s your favorite feature?

Follow for more deep dives into Java, JVM performance, and productivity tools. ☕💻

Top comments (0)