Oracle Releases Java 21
September 19, 2023

Oracle announced the availability of Java 21.

Java 21 (Oracle JDK 21) delivers thousands of performance, stability, and security improvements, including platform enhancements that will help developers increase productivity and drive innovation and growth across their organizations.

"Java continues to be the language and platform of choice for the development of robust, scalable, and secure applications used by organizations and millions of individuals around the world," said Georges Saab, SVP of Oracle Java Platform and chair of the OpenJDK governing board. "The new enhancements in Java 21 enable developers to build better applications even faster than before. In addition, commercial support will be available for at least eight years to enable customers to migrate at their own pace."

The latest Java Development Kit (JDK) provides updates and improvements with 15 JDK Enhancement Proposals (JEPs). JDK 21 delivers language improvements from OpenJDK project Amber (String Templates, Record Patterns, Pattern Matching for Switch, Unnamed Patterns and Variables, and Unnamed Classes and Instance Main Methods); enhancements from Project Panama (Foreign Function & Memory API and Vector API); features related to Project Loom (Virtual Threads, Scoped Values, and Structured Concurrency); performance updates (Generational ZGC); and maintenance and deprecation features (Deprecate the 32-bit x86 Port for Removal, and Prepare to Disallow the Dynamic Loading of Agents).

Oracle will offer long term support for Java 21 for at least eight years. This extended support period gives organizations flexibility to keep applications in production longer with minimal maintenance, and to eventually migrate on their own terms. Based on customer feedback and use in the Java ecosystem, Oracle has also announced that long term support for Java 11 has been extended through at least January 2032, providing at least eight more years of support and updates from Oracle.

Significant updates delivered in Java 21 are:

- JEP 444: Virtual Threads: Significantly streamlines the process of writing, maintaining, and observing high-throughput, concurrent applications by introducing lightweight virtual threads to the Java Platform. By enabling developers to easily troubleshoot, debug, and profile concurrent applications and scale them with existing JDK tools and techniques, virtual threads help accelerate application development.

- JEP 446: Scoped Values (Preview): Enables the sharing of immutable data within and across threads. This helps increase the ease-of-use, comprehensibility, robustness, and performance of developers' projects.

- JEP 453: Structured Concurrency (Preview): Simplifies concurrent programming by introducing an API for structured concurrency, which helps promote a style of concurrent programming that can eliminate common risks arising from cancellation and shutdown – such as thread leaks and cancellation delays – and improves the observability of concurrent code. This helps developers streamline error handling and cancellation, improve reliability, and enhance observability.

- JEP 439: Generational ZGC: Improves application performance by extending the Z Garbage Collector (ZGC) to maintain separate generations for young and old objects. Generational ZGC helps improve developer productivity by lowering the overhead of required heap memory and garbage collection CPU for applications, as well as reducing the risks of allocation stalls.

- JEP 430: String Templates (Preview): Simplifies the development of Java programs by making it easy to express strings that include values computed at run time, and improves the security of programs that compose strings from user-provided values and pass them to other systems. In addition, the readability of expressions that mix text and expressions is enhanced, and non-string values computed from literal text and embedded expressions can be created without having to transit through an intermediate string representation. This helps increase developer productivity by making the Java language more readable, writable, and maintainable.

- JEP 440: Record Patterns (Third Preview): Enhances the Java language by extending pattern matching to destructure instances of record classes, as well as enabling the addition of nested patterns. This enables developers to extend pattern matching to more sophisticated and composable data queries, which helps increase productivity.

- JEP 441: Pattern Matching for Switch: Expands the expressiveness and applicability of switch expressions and statements by allowing patterns to appear in case labels. In addition, the safety of switch statements is increased by requiring that pattern switch statements cover all possible input values, and all existing switch expressions and statements can continue to be compiled with no changes and executed with identical semantics. This helps developers streamline and increase the reliability of their projects by making the Java language more semantic so that complex data-oriented queries can be expressed concisely and safely.

- JEP 443: Unnamed Patterns and Variables (Preview): Enhances the Java language by enabling unnamed patterns to match a record component without stating the component's name or type, as well as unnamed variables that can be initialized but not used. This helps simplify the development process by increasing the readability of record patterns and improving the maintainability of all code.

- JEP 445: Unnamed Classes and Instance Main Methods (Preview): Helps simplify and improve the accessibility of the Java language so that educators can introduce programming concepts in a gradual manner. By avoiding the introduction of a separate beginner's dialect of Java and a separate beginner's toolchain, student programs can be compiled and run with the same tools that compile and run any Java program – helping students write basic programs in a concise manner and grow their code gracefully as their skills increase. This helps improve student developer productivity by enabling them to write their first programs without needing to understand language features designed for large programs.

- JEP 442: Foreign Function & Memory API (Third Preview): Introduces an API to enable Java programs to interoperate with code and data outside of the Java runtime. By efficiently invoking foreign functions (i.e., code outside the Java Virtual Machine [JVM]), and by safely accessing foreign memory (i.e., memory not managed by the JVM), the new API enables Java programs to call native libraries and process native data without requiring the Java Native Interface. This increases ease-of-use, flexibility, performance, and safety for developers.

- JEP 448: Vector API (Sixth Incubator): Introduces an API to express vector computations that reliably compile at runtime to vector instructions on supported CPU architectures. This helps developers improve the performance of their projects by providing them with access to a API that is capable of clearly and concisely expressing a wide range of vector computations.

The Java 21 release is the result of extensive collaboration between Oracle engineers and other members of the worldwide Java developer community via OpenJDK and the Java Community Process (JCP). In addition to the new enhancements, Java 21 is supported by Java Management Service (JMS) – an Oracle Cloud Infrastructure (OCI) native service – which provides a unified console and dashboard to help organizations manage Java runtimes and applications on-premises or on any cloud. For more details on the features in Java 21, please read the Java 21 technical blog post.

Java delivers optimal performance, efficiency, and innovation when deployed in the cloud on OCI, and OCI is one of the first hyperscale clouds to support Java 21. In addition, customers gain cost savings at scale by running Java on OCI. Oracle Java SE, Oracle GraalVM, and the Java SE Subscription Enterprise Performance Pack are available free of charge on OCI, enabling developers to build and deploy applications that run faster, better, and with optimized cost-performance.

The Oracle Java Universal SE Subscription is a pay-as-you-go offering that provides customers with best-in-class support, including triage support for their entire Java portfolio, entitlement to GraalVM, the Java SE Subscription Enterprise Performance Pack, access to the advanced features of the Java Management Service, and the flexibility to upgrade at the pace of their businesses. This helps IT organizations manage complexity, contain costs, and mitigate security risks.

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