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What Are the Java 17 New Features?

What Are the Java 17 New Features?

  • Sealed Classes: Restricts class extensions for better hierarchy control.
  • Pattern Matching for Switch: Simplifies type checks in switch statements.
  • Text Blocks: Handles multi-line strings more cleanly and readably.
  • Foreign Function and Memory API: Access native code and memory efficiently.
  • Improved Garbage Collectors: ZGC, Shenandoah, and updated G1 GC.

What Are the Java 17 New Features?

Java 17 New Features

Java 17, released in September 2021, is a Long-Term Support (LTS) release that marks a significant milestone in Java’s evolution. With its introduction, Java 17 introduces numerous innovative features, refinements, and tools to improve developer productivity, application performance, and overall platform modernization.

This version solidifies Java’s position as a leading enterprise and modern application development choice.

Let’s explore the most notable features introduced in Java 17 in greater detail.


1. Sealed Classes

What are Sealed Classes? Sealed classes allow developers to control which classes or interfaces can extend or implement them, enforcing a more predictable and secure class hierarchy.

Key Benefits:

  • Ensures stricter inheritance rules, reducing potential errors.
  • Enhances readability by explicitly defining permitted subclasses.
  • Supports better code maintainability by preventing unexpected extensions.

Example:

public sealed class Shape permits Circle, Rectangle {
    // Base class
}

public final class Circle extends Shape {
    // Circle implementation
}

public final class Rectangle extends Shape {
    // Rectangle implementation
}

Sealed classes provide developers the tools to build safer and more explicit API contracts, simplifying debugging and extending class relationships.


2. Pattern Matching for Switch (Preview)

What is Pattern Matching for Switch? This feature elevates the switch statement by directly allowing patterns and type checks within cases, making the syntax more expressive and less error-prone.

Key Benefits:

  • Eliminates the need for verbose type checks and casts.
  • Simplifies complex decision-making logic in applications.
  • Improves maintainability by reducing boilerplate code.

Example:

switch (obj) {
    case String s -> System.out.println("String: " + s);
    case Integer i -> System.out.println("Integer: " + i);
    case null -> System.out.println("Null value");
    default -> System.out.println("Unknown type");
}

Pattern matching for switchDevelopers can write concise and efficient conditional logic, which is particularly useful in scenarios involving polymorphic objects or dynamic typing.


3. Text Blocks (Standardized)

What are Text Blocks? Text blocks simplify creating and managing multi-line strings by providing cleaner syntax. They were first introduced as a preview in earlier versions and are now standardized in Java 17.

Key Benefits:

  • Enhances the readability of multi-line strings, particularly for JSON, XML, or SQL.
  • Reduces the need for escape sequences and manual concatenation.
  • Improves consistency and ease of editing for string-heavy applications.

Example:

String json = """
{
    "name": "Java",
    "version": 17
}
""";

This feature is especially useful for applications dealing with structured data formats, improving development speed and code clarity.


4. Enhanced Pseudo-Random Number Generators (PRNGs)

What’s New? Java 17 introduces robust interfaces and implementations for random number generation, providing more flexibility, improved algorithms, and better support for parallel computation.

Key Benefits:

  • Offers a standardized API for diverse PRNG algorithms.
  • Introduces splittable and jumpable generators for concurrent applications.
  • Improves performance in computational simulations and statistical modeling.

Example:

RandomGenerator generator = RandomGenerator.of("Xoshiro256PlusPlus");
System.out.println(generator.nextInt());

Developers building scientific, financial, or gaming applications can now leverage PRNG enhancements for faster and more accurate computations.


5. Foreign Function and Memory API (Preview)

What is it? This API replaces the outdated Java Native Interface (JNI). It allows Java programs to interact directly with native code and memory, offering better performance and usability.

Key Benefits:

  • Simplifies working with native libraries and memory management.
  • Reduces the risk of memory leaks and pointer-related errors.
  • Enhances performance for applications that integrate with external systems.

Example:

try (MemorySegment segment = MemorySegment.allocateNative(1024)) {
    segment.setAtIndex(ValueLayout.JAVA_INT, 0, 42);
    System.out.println(segment.getAtIndex(ValueLayout.JAVA_INT, 0));
}

This feature is invaluable for high-performance applications requiring direct integration of low-level systems or native APIs.


6. Deprecations and Removals

What has changed? Java 17 modernizes its platform by deprecating and removing outdated features and tools, streamlining the language and JVM.

Key Highlights:

  • Removal of AOT (Ahead-of-Time) and JIT compilers as experimental features.
  • Deprecation of the Applet API, marking the end of an era for browser-based Java.
  • Elimination of the RMI Activation System, reflecting changes in distributed application design.

Impact: These updates simplify the codebase and encourage developers to adopt modern, more efficient paradigms.


7. JEP 356: Enhanced JFR Event Streaming

What is Enhanced JFR Streaming? Java Flight Recorder (JFR) now supports continuous streaming of diagnostic events, making real-time monitoring and analyzing applications easier.

Key Benefits:

  • Enables real-time performance monitoring.
  • Reduces overhead for profiling and diagnostics in production systems.
  • Improves application observability and debugging capabilities.

Example:

var stream = FlightRecorder.startStreaming();
stream.onEvent("jdk.GarbageCollection", System.out::println);

Enhanced JFR Streaming is a boon for enterprise applications where performance monitoring and debugging are critical.


8. Stronger Encapsulation of JDK Internals

What’s Changed? Java 17 reinforces the encapsulation of internal APIs, promotes standard APIs, and reduces dependency on unsupported internal classes.

Key Benefits:

  • Encourages best practices by limiting access to internal APIs.
  • Reduces risks of breaking changes in future Java versions.

Example: Developers are now encouraged to migrate to robust alternatives java.util.concurrent rather than relying on internal implementations.


9. Deprecation of Security Manager

What is the Security Manager? Java 17 deprecates the security manager, once used to restrict application access to system resources.

The Key Reason is that it is rarely used in modern applications and has been rendered obsolete by advancements in other security mechanisms.

Impact: Developers relying on the Security Manager must explore alternative, modern security strategies.


10. Performance Improvements

What’s Improved? Java 17 introduces significant performance enhancements across the JVM and libraries, targeting key areas like:

  • Garbage Collection: Enhanced G1, ZGC, and Shenandoah collectors reduce latency and improve scalability.
  • Startup Times: Faster application initialization improves developer workflows.
  • Hardware Utilization: Optimized for modern multi-core processors and large memory systems.

Key Benefits:

  • Reduced latency for real-time and low-latency applications.
  • Improved throughput for large-scale enterprise workloads.
  • Better resource utilization for cloud-native and containerized environments.

Read more in detail about how Java 8 compares to Java 17 in terms of performance.


Conclusion

Java 17 brings many innovative features and improvements, making it a compelling choice for modern development. From sealed classes and pattern matching to advanced garbage collectors and the Foreign Function and Memory API, this release offers significant upgrades in performance, productivity, and compatibility.

As a Long-Term Support release, Java 17 is well-suited for organizations looking to modernize their applications while ensuring stability and reliability for years.

FAQ: What Are the Java 17 New Features?

What are sealed classes in Java 17?
Sealed classes allow developers to control which classes can extend or implement them, ensuring a well-defined inheritance hierarchy.

How does pattern matching for the switch improve coding?
Pattern matching for switches reduces boilerplate by directly allowing type checks and patterns in switch cases, making code cleaner and more readable.

What are text blocks, and why are they useful?
Text blocks simplify handling multi-line strings by removing the need for escape sequences and concatenation, improving string management in Java.

What is the Foreign Function and Memory API?
It’s a modern API that replaces JNI. It enables direct interaction with native code and memory and offers better performance and safety.

What garbage collectors are introduced in Java 17?
Java 17 includes ZGC and Shenandoah for low-latency applications and an improved G1 GC as the default collector.

What security improvements are in Java 17?
Java 17 deprecates the Security Manager, focusing on alternative mechanisms and includes optimized cryptographic algorithms.

Are there any deprecated features in Java 17?
Yes, Java 17 removes AOT and JIT compilers, the Applet API, and the RMI Activation System to modernize the platform.

What are the performance benefits of Java 17?
Java 17 offers faster startup times, optimized garbage collectors, and better support for modern hardware, improving application performance.

How does Java 17 handle native memory?
The Foreign Function and Memory API allows safer and more efficient native memory access, replacing older methods like JNI.

What is the significance of enhanced JFR event streaming?
It enables real-time monitoring of applications by continuously streaming Java Flight Recorder events with minimal overhead.

What changes were made to JDK internals in Java 17?
Java 17 strengthens encapsulation by restricting access to internal APIs, encouraging developers to use supported alternatives.

How does Java 17 improve support for random number generation?
Java 17 introduces new PRNG algorithms, such as Xoshiro256PlusPlus, and splittable generators for parallel computation.

Has the Security Manager been removed completely in Java 17?
No, it is deprecated but not removed. Developers are encouraged to explore modern security alternatives.

Why are Applets deprecated in Java 17?
The Applet API is outdated and no longer relevant in modern web development, leading to its removal.

Should developers upgrade to Java 17?
Java 17 is a Long-Term Support (LTS) release with modern features, improved performance, and extended stability, making it ideal for upgrading.

Author
  • Fredrik Filipsson has 20 years of experience in Oracle license management, including nine years working at Oracle and 11 years as a consultant, assisting major global clients with complex Oracle licensing issues. Before his work in Oracle licensing, he gained valuable expertise in IBM, SAP, and Salesforce licensing through his time at IBM. In addition, Fredrik has played a leading role in AI initiatives and is a successful entrepreneur, co-founding Redress Compliance and several other companies.

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