Feature Summary: Java SE 17

Tools

Java SE 17 introduced several tools and utilities aimed at enhancing developer productivity and simplifying the development process.

• Microbenchmark Suite: Provides a suite of microbenchmarks to help developers benchmark the performance of Java APIs and features (JEP 230).
• Packaging Tool: Introduces the jpackage tool to package Java applications into platform-specific packages, facilitating application deployment (JEP 392).
• JFR Event Streaming: Extends Java Flight Recorder (JFR) to provide a continuous stream of events with minimal performance impact (JEP 349).

Java Syntax

This category includes fundamental changes and updates to the Java programming language, enhancing readability and reducing boilerplate code.

• Switch Expressions: Standardises switch expressions and introduces the yield statement to return a value from switch expressions (JEP 361).
• Pattern Matching for instanceof: Simplifies the instanceof operator to eliminate the need for manual type casting in many cases, enhancing code readability and reducing boilerplate (JEP 394).
• Records: Provides a compact syntax for declaring classes that are transparent holders for shallowly immutable data (JEP 395).
• Sealed Classes: To restrict which other classes or interfaces may extend or implement them, enhancing control over API design (JEP 409).
• Text Blocks: For multi-line string literals that minimize the need for most escape sequences, simplifying the authoring of JSON and SQL queries (JEP 355).
• Warnings for Value-Based Classes: Generates warnings for any attempt to synchronize on instances of value-based classes, discouraging incorrect usage patterns (JEP 390).

Libraries

Enhancements and additions to the Java standard API, providing new capabilities and simplifying common tasks.

• Enhanced Pseudo-Random Number Generators: Enhances the pseudo-random number generators in Java, providing new interfaces and implementations for random number generation (JEP 356).
• Unix-Domain Socket Channels: Adds support for Unix-domain (local) socket channels that allow inter-process communication on the same host more efficiently than TCP/IP (JEP 380).
• Reimplement the Legacy Socket API: Replaces the underlying implementation used by the java.net.Socket and java.net.ServerSocket APIs to improve simplicity and maintainability (JEP 353).
• Reimplement the Legacy DatagramSocket API: Updates the older DatagramSocket API with a simpler, more modern implementation, similar to the stream socket API (JEP 373).

Performance & Security

Updates and improvements to the JVM and garbage collection, focusing on performance, security, and robustness.

• Dynamic CDS Archives: Adds dynamic archiving of classes at the end of application execution to improve startup time for subsequent executions (JEP 350).
• Default CDS Archives: Enhances the JDK build process to generate a class data-sharing (CDS) archive, which can improve startup time (JEP 341).
• JVM Constants API: Introduces an API to model nominal descriptions of key class-file and run-time artifacts, primarily for the benefit of compilers and tools (JEP 334).
• Abortable Mixed Collections for G1: Improves G1 garbage collector to abort mixed collections if they exceed a certain duration, improving efficiency (JEP 344).
• Promptly Return Unused Committed Memory from G1: Enhances G1 to more promptly return unused Java heap memory to the operating system during full GC cycles (JEP 346).
• NUMA-Aware Memory Allocation for G1: Enables G1 to automatically respect the NUMA topology of the system, improving performance on NUMA-capable systems (JEP 345).
• Hidden Classes: Introduces hidden classes that cannot be used directly by the bytecode of other classes, intended for frameworks that generate classes at runtime (JEP 371).
• Shenandoah: A Low-Pause-Time Garbage Collector: A low-pause-time garbage collector to reduce GC pause times by performing more garbage-collection work concurrently with the application threads (JEP 379).
• ZGC: A Scalable Low-Latency Garbage Collector: A scalable low-latency garbage collector (ZGC) to reduce pause times during GC without compromising throughput (JEP 377).
• Concurrent Thread-Stack Processing in ZGC: Enhances ZGC to process thread stacks concurrently with other GC operations, reducing pause times further (JEP 376).
• Edwards-Curve Digital Signature Algorithm (EdDSA): Adds a cryptographic algorithm that provides security equivalent to other NIST P-256 algorithms but faster (JEP 339).
• Elastic Metaspace: Reduces the metaspace footprint of Java applications by returning unused class metadata memory to the operating system more promptly (JEP 387).
• Strongly Encapsulate JDK Internals: Strengthens the encapsulation of JDK internal APIs to prevent their use by external APIs, improving JDK security and maintainability (JEP 403).
• Remove the Experimental AOT and JIT Compiler: Removes the experimental ahead-of-time (AOT) and just-in-time (JIT) compiler, simplifying the JDK and focusing on more broadly used features (JEP 410).
• Context-Specific Deserialization Filters: Enhances security by allowing applications to configure context-specific filters for deserialization, reducing the risk of deserialization vulnerabilities (JEP 415).

Other

• Enable C++14 Language Features: Updates the JDK’s C++ source code to use C++14 language features, improving JDK’s security and maintainability (JEP 347).
• Migrate from Mercurial to Git: Moves all OpenJDK source code repositories from Mercurial to Git, facilitating version control with modern tooling (JEP 357).
• Migrate to GitHub: Transfers all Git repositories to GitHub, enhancing the collaboration and contribution process for the OpenJDK community (JEP 369).
• Windows/AArch64 Port: Adds support for Windows on the AArch64 architecture, ensuring Java can run on modern ARM-based Windows devices (JEP 388).
• macOS/AArch64 Port: Adds support for macOS on AArch64, enabling Java to run on new Apple Silicon (M1) Macs (JEP 391).