What is new in java 17 after java 18

Java 17 and Java 18 introduced several new features and improvements, but because Java 17 is a Long-Term Support (LTS) release, it’s considered a more stable and supported version over a longer period than Java 18, which is a regular release with a shorter support cycle. Here’s a breakdown of significant changes in Java 17 compared to Java 18:

Key Features in Java 17 (LTS)

Java 17, released in September 2021, is a long-term support version with multiple enhancements and optimizations over previous versions, including features that were first incubated in Java 16.

1. Sealed Classes (Standardized):
   • Sealed classes, introduced in Java 15 as a preview, allow you to restrict which classes can extend or implement a particular class/interface. This adds control to inheritance hierarchies.
     
     Java

     public sealed class Shape permits Circle, Rectangle {}

     1	public sealed class Shape permits Circle, Rectangle {}

2. Pattern Matching for switch (Preview):
   • Extends pattern matching to the switch statement, enabling more flexible and expressive control structures.
     
     Java

     switch (obj) { case String s -> System.out.println("String: " + s); case Integer i -> System.out.println("Integer: " + i); default -> System.out.println("Default case"); }

     1 2 3 4 5

     switch (obj) { case String s -> System.out.println("String: " + s); case Integer i -> System.out.println("Integer: " + i); default -> System.out.println("Default case"); }

3. Foreign Function & Memory API (Incubator):
   • Introduced a new API to access native code and memory more easily and safely, as an alternative to JNI (Java Native Interface).
4. Removal of Deprecated APIs:
   • Removed the RMI Activation, Applet API (no longer used widely), and support for the SecurityManager.
5. Strong Encapsulation in the JDK:
   • The Java Platform now enforces strong encapsulation, making it harder to access internal JDK classes and packages, unless explicitly opened.
6. macOS/AArch64 Support:
   • Added support for running Java on Apple’s ARM-based M1 processors, enhancing Java’s cross-platform capabilities.
7. Enhanced Pseudo-Random Number Generators:
   • Introduced new interfaces and implementations for random number generation, supporting stream-based approaches and a more extensible framework.

Key Features in Java 18

Java 18, released in March 2022, brought several new features, though it’s a non-LTS release with a shorter support cycle. Java 18 continued to build on features previewed or incubated in earlier versions and made further refinements.

1. UTF-8 by Default:
   • The default character encoding has changed to UTF-8. This makes applications more portable, as encoding inconsistencies across platforms are reduced.
2. Simple Web Server:
   • Java 18 introduced a simple HTTP file server for quick testing and prototyping. It’s intended for developers who need a lightweight solution for serving files over HTTP.
     
     $ java -m jdk.httpserver

     1	$ java -m jdk.httpserver

3. Code Snippets in Javadoc:
   • Introduced support for snippets in Javadoc (@snippet) to add code examples directly in documentation comments, making it easier to create and maintain documentation with embedded, validated code.
4. Pattern Matching for switch (Second Preview):
   • Improved upon the switch pattern matching from Java 17, allowing more expressive and type-safe pattern matching.
5. Foreign Function & Memory API (Second Incubator):
   • The Foreign Function & Memory API was refined in Java 18, allowing easier and safer interaction with native code, reducing the need for JNI.
6. Vector API (Third Incubator):
   • The Vector API, introduced in earlier versions, was further incubated to improve the performance of computations that can benefit from SIMD (Single Instruction, Multiple Data) instructions.
7. Internet-Address Resolution SPI:
   • Java 18 added a new service-provider interface for hostname and IP address resolution. This provides more control over how the JVM resolves IP addresses, improving the customizability of network operations.
8. Deprecation of Finalization:
   • Finalization, a mechanism used for object cleanup before garbage collection, has been deprecated. It was often unpredictable and error-prone, and alternatives like try-with-resources and Cleaner were introduced in prior versions.

Summary of Java 17 vs. Java 18 Enhancements

Choosing Between Java 17 and Java 18

• Java 17 (LTS) is best for stability and long-term support, as it receives regular updates and support for many years. Organizations looking for stability in production environments typically choose Java 17.
• Java 18 brings new experimental and preview features that continue to evolve Java’s capabilities but isn’t intended for long-term deployment. It’s useful for development environments where access to the latest language improvements and APIs is desired, especially for prototyping and testing.

Each version introduces advancements in performance, usability, and safety, pushing Java forward while retaining backward compatibility and stability, especially in LTS releases.