Java 17 Features : What’s New and Why It Matters

Java has long stood as a cornerstone in the software development ecosystem. With every new version, developers eagerly anticipate updates that enhance performance, introduce powerful new language constructs, and simplify coding practices. Among all Java versions released in recent years, Java 17 features a powerful blend of stability and innovation, making it one of the most important Long-Term Support (LTS) releases to date.

This blog explores the most significant additions and improvements introduced in Java 17, complete with practical examples to help you understand and apply them in real-world scenarios.

Why Java 17 Matters

Java 17, released in September 2021, is an LTS version. This means it will receive extended support from Oracle and other vendors until at least 2029. LTS releases are critical for businesses and developers looking for a stable and secure development platform.

The new Java 17 features are a mix of finalized JEPs (JDK Enhancement Proposals), preview capabilities, and deprecated functionalities, all designed to modernize the language while preserving Java’s legacy of reliability.

Sealed Classes (JEP 409)

Sealed classes allow developers to define a restricted hierarchy, giving them more control over which classes or interfaces can extend or implement another class. This promotes a cleaner and more predictable architecture, especially in large systems.

public sealed class Vehicle permits Car, Truck {}

final class Car extends Vehicle {}
final class Truck extends Vehicle {}

In this example, only Car and Truck are permitted to extend Vehicle. Any attempt to create another subclass will result in a compilation error.

Pattern Matching for instanceof (JEP 394)

Pattern matching simplifies the common process of casting an object after performing an instanceof check.

Old Way

if (obj instanceof String) {
    String str = (String) obj;
    System.out.println(str.length());
}

New Way

if (obj instanceof String str) {
    System.out.println(str.length());
}

This new pattern reduces boilerplate and makes code more readable and type-safe.

Enhanced Switch Statements – Preview (JEP 406)

Java 17 continues to refine pattern matching for switch, introduced as a preview. It allows switching on patterns instead of raw values, bringing more flexibility and clarity to complex conditions.

static String formatter(Object obj) {
    return switch (obj) {
        case Integer i -> "Integer: " + i;
        case String s -> "String: " + s;
        case null -> "Null object";
        default -> "Unknown type";
    };
}

This makes the switch statement more expressive and easier to extend.

JEP 356: Enhanced Pseudo-Random Number Generators

Java 17 introduces a new interface, RandomGenerator, and several implementations for different algorithms, such as Xoshiro256PlusPlus and L64X128MixRandom.

import java.util.random.RandomGenerator;
import java.util.random.RandomGeneratorFactory;

public class RandomExample {
    public static void main(String[] args) {
        RandomGenerator gen = RandomGeneratorFactory.of("L64X128MixRandom").create();
        System.out.println(gen.nextInt());
    }
}

These new classes provide improved random number generation performance and security.

Strong Encapsulation of JDK Internals (JEP 403)

One of the most impactful Java 17 features is the strong encapsulation of internal elements of the JDK. APIs in non-exported packages can no longer be accessed using reflection unless explicitly permitted.

Implication:

• Libraries relying on internal APIs will fail unless updated.
• Forces developers to stick to official, documented APIs—leading to better security and maintainability.

Deprecations and Removals

Java 17 also removes or deprecates several outdated features:

• Security Manager: Marked as deprecated for removal (JEP 411).
• Applet API: Deprecated due to obsolete browser support.
• RMI Activation System: Removed due to lack of modern usage.

These changes streamline the language and remove legacy baggage.Foreign Function & Memory API (Incubator)

Although still in incubation, this API is a game changer for developers needing to interact with native code and memory safely—without using JNI.

// Example using the MemorySegment API (pseudo-code)
try (MemorySegment segment = MemorySegment.allocateNative(100)) {
    // Manipulate native memory safely
}

It opens the door for better performance in data-intensive and system-level applications.

Performance Improvements

Java 17 features several JVM-level enhancements:

• Improved startup time with optimized class loading
• Reduced garbage collection overhead via ZGC and G1 updates
• Smaller memory footprint with compressed class pointers and code cache sharing

These improvements help applications scale more efficiently, especially in containerized and cloud environments.

Platform-Specific Enhancements

Java 17 adds support for:

• macOS/AArch64 (Apple Silicon)
• Windows/AArch64 (ARM-based systems)

This reflects the language’s commitment to cross-platform compatibility, ensuring that Java runs smoothly on modern hardware.

Tools That Support Java 17

Major tools and frameworks already support Java 17:

• Spring Boot 3.x
• Maven 3.8+
• Gradle 7.3+
• Hibernate 6+
• Micronaut
• Apache Tomcat 10+

IDEs:

• IntelliJ IDEA (2021.2+)
• Eclipse (2021-09 release)
• VS Code (Java Extension Pack)

How to Use Java 17 Features in Your Project

Java 17 Download. To start using the new Java 17 capabilities:

1. Download the java jdk 17 from:
   • Oracle
   • OpenJDK
   • Adoptium Temurin
2. Configure your build tools (Maven, Gradle) to target version 17.
3. Update your IDE or development environment to support Java 17.

Java 17 in the Real World

Many large enterprises and cloud providers are now defaulting to Java 17 for production applications. Its stability, performance, and backward compatibility make it a smart choice for mission-critical systems.

With support for modern paradigms like pattern matching and sealed classes, Java 17 features also make it more enjoyable and productive for developers building microservices, APIs, and large-scale platforms.

Final Thoughts

Java 17 features are a testament to the platform’s maturity and adaptability. By integrating new constructs, removing outdated components, and optimizing runtime behavior, Java 17 stands as a milestone in the language’s evolution.

Whether you’re working on enterprise software, mobile backends, or cutting-edge cloud applications, now is the perfect time to migrate or start with Java 17.

💡 Pro Tip: For future compatibility and smoother upgrades, familiarize yourself with Java 21—the next LTS version—as it builds upon the solid foundation laid by Java 17.

Tags: Java 17 features, Java 17 examples, Java sealed classes, Java 17 vs Java 11, pattern matching Java, Java development, Java upgrade, JDK 17, Java switch enhancements

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