Java 25 New Features: Complete Guide with Examples and Best Practices

The Java 25, released in September 2025, is the new LTS (Long-Term Support) version of the Java platform. This version consolidates various features that were in preview or incubation in previous versions, bringing significant improvements in productivity, performance, security, and observability.

In this article, you will learn about the main new features of Java 25, with practical code examples, clear explanations, and official references for deeper understanding.

🚀 Main New Features of Java 25

✅ Compact Source Files and Instance Main Methods (JEP 512)

It is now possible to write Java programs much more simply, without the need to declare a public class or the public static void main method.

This makes Java more friendly for scripts, quick examples, and learning.

Example:

void main() {
    IO.println("Hello, Java 25!");
}

You can run it directly with:

java Hello.java

🧩 Flexible Constructor Bodies (JEP 513)

Java 25 allows adding logic before the call to super() in constructors. This facilitates validations and makes the code more expressive.

Example:

class User {
    String name;

    User(String name) {
        if (name == null || name.isBlank()) {
            throw new IllegalArgumentException("Invalid name");
        }
        super();
        this.name = name;
    }
}

🔍 Pattern Matching with Primitive Types (Preview – JEP 507)

Java now starts to allow the use of primitive types in instanceof and switch, reducing repetitive code.

Example:

static void process(Object value) {
    if (value instanceof int i) {
        System.out.println("Integer value: " + i);
    }
}

⚠️ Feature still in preview, use with caution in production.

🔐 New APIs and Security

🔑 Key Derivation Function API (JEP 510)

Java 25 adds native support for key derivation algorithms such as PBKDF2, improving security and reducing dependency on external libraries.

Example:

KeySpec spec = new PBEKeySpec(
    "password".toCharArray(),
    salt,
    65536,
    256
);

SecretKeyFactory factory =
    SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");

byte[] hash = factory.generateSecret(spec).getEncoded();

🧵 Modern Concurrency

Scoped Values (JEP 506)

The Scoped Values emerge as a safer and more efficient alternative to ThreadLocal, especially in applications with Virtual Threads.

Example:

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

ScopedValue.where(USER, "Eridani").run(() -> {
    System.out.println("Current user: " + USER.get());
});

⚙️ Performance and Runtime

⚡ Compact Object Headers (JEP 519)

Reduction of the size of object headers in memory, resulting in:

• Lower RAM consumption
• Better cache usage
• Performance gains in applications with many objects

🧹 Generational Shenandoah GC (JEP 521)

The Shenandoah Garbage Collector is now generational, reducing pauses and improving throughput, ideal for high-scale systems.

🚀 Improvements in AOT (Ahead-of-Time)

Java 25 brings improvements in AOT cache generation, helping to reduce application startup time.

java -XX:AOTCacheOutput=app.aot -jar app.jar

📊 Observability with Java Flight Recorder (JFR)

The JFR has received important improvements:

• CPU time measurement
• Cooperative sampling
• Better method traceability

These features facilitate performance analysis in production.

📈 When is it worth migrating to Java 25?

✔ New projects

✔ Serverless applications

✔ Systems that need better performance and observability

⚠️ Carefully evaluate the use of preview features in critical environments.

🔗 Official References

• Oracle – Java 25 Release Notes
• https://www.oracle.com/java/technologies/javase/25-relnote-issues.html
• Baeldung – Java 25 Features
• https://www.baeldung.com/java-25-features
• OpenJDK – JEPs of Java 25
• https://openjdk.org/projects/jdk/25/
• Java Guides – New Features in Java 25
• https://www.javaguides.net/2025/09/new-features-in-java-25.html

🧠 Conclusion

The Java 25 reinforces the platform's commitment to modernization, performance, and productivity. As an LTS version, it is an excellent choice for new projects and a strong candidate for migrating from previous versions like Java 17 or 21.

If you work with Java daily, it is worth exploring these new features and starting to test them now.