Key: JDK-X - https://bugs.openjdk.java.net/browse/JDK-X CVE-XXXX-YYYY: https://cve.mitre.org/cgi-bin/cvename.cgi?name=XXXX-YYYY New in release OpenJDK 21.0.0 (2023-09-XX): =========================================== Major changes are listed below. Some changes may have been backported to earlier releases following their first appearance in OpenJDK 21. The full list of changes in 21u can be found at: - * https://builds.shipilev.net/backports-monitor/release-notes-21.txt NEW FEATURES ============ Language Features ================= Pattern Matching for switch =========================== https://openjdk.org/jeps/406 https://openjdk.org/jeps/420 https://openjdk.org/jeps/427 https://openjdk.org/jeps/433 https://openjdk.org/jeps/441 Enhance the Java programming language with pattern matching for `switch` expressions and statements, along with extensions to the language of patterns. Extending pattern matching to `switch` allows an expression to be tested against a number of patterns, each with a specific action, so that complex data-oriented queries can be expressed concisely and safely. This was a preview feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 17 (JEP 406), which saw a second preview in OpenJDK 18 (JEP 420), a third in OpenJDK 19 (JEP 427) and a fourth (JEP 427) in OpenJDK 20. It became final with OpenJDK 21 (JEP 441). Record Patterns =============== https://openjdk.org/jeps/405 https://openjdk.org/jeps/432 https://openjdk.org/jeps/440 Enhance the Java programming language with record patterns to deconstruct record values. Record patterns and type patterns can be nested to enable a powerful, declarative, and composable form of data navigation and processing. This was a preview feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 19 (JEP 405) with a second preview (JEP 432) in OpenJDK 20. It became final with OpenJDK 21 (JEP 440). String Templates ================ https://openjdk.org/jeps/430 Enhance the Java programming language with string templates. String templates complement Java's existing string literals and text blocks by coupling literal text with embedded expressions and template processors to produce specialized results. This is a preview feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 21 (JEP 430). Unnamed Patterns and Variables ============================== https://openjdk.org/jeps/443 Enhance the Java language with unnamed patterns, which match a record component without stating the component's name or type, and unnamed variables, which can be initialized but not used. Both are denoted by an underscore character, _. This is a preview feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 21 (JEP 443). Unnamed Classes and Instance Main Methods ========================================= https://openjdk.org/jeps/445 Evolve the Java language so that students can write their first programs without needing to understand language features designed for large programs. Far from using a separate dialect of Java, students can write streamlined declarations for single-class programs and then seamlessly expand their programs to use more advanced features as their skills grow. This is a preview feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 21 (JEP 445). Library Features ================ Vector API ========== https://openjdk.org/jeps/338 https://openjdk.org/jeps/414 https://openjdk.org/jeps/417 https://openjdk.org/jeps/426 https://openjdk.org/jeps/438 https://openjdk.org/jeps/448 Introduce an API to express vector computations that reliably compile at runtime to optimal vector hardware instructions on supported CPU architectures and thus achieve superior performance to equivalent scalar computations. This is an incubation feature (https://openjdk.java.net/jeps/11) introduced in OpenJDK 16 (JEP 338). A second round of incubation took place in OpenJDK 17 (JEP 414), OpenJDK 18 (JEP 417) saw a third, OpenJDK 19 a fourth (JEP 426), OpenJDK 20 (JEP 438) a fifth and OpenJDK 21 a sixth (JEP 448). Foreign Function & Memory API ============================= https://openjdk.org/jeps/412 https://openjdk.org/jeps/419 https://openjdk.org/jeps/424 https://openjdk.org/jeps/434 https://openjdk.org/jeps/442 Introduce an API by which Java programs can interoperate with code and data outside of the Java runtime. By efficiently invoking foreign functions (i.e., code outside the JVM), and by safely accessing foreign memory (i.e., memory not managed by the JVM), the API enables Java programs to call native libraries and process native data without the brittleness and danger of JNI. This API is now a preview feature (http://openjdk.java.net/jeps/12). It was first introduced in incubation (https://openjdk.java.net/jeps/11) in OpenJDK 17 (JEP 412), and is an evolution of the Foreign Memory Access API (OpenJDK 14 through 16) and Foreign Linker API (OpenJDK 16) (see release notes for java-17-openjdk). OpenJDK 18 saw a second round of incubation (JEP 419) before its inclusion as a preview in OpenJDK 19 (JEP 424) and a second in OpenJDK 20 (JEP 434). It reaches a third preview in OpenJDK 21 (JEP 442). Virtual Threads =============== https://openjdk.org/jeps/425 https://openjdk.org/jeps/436 https://openjdk.org/jeps/444 Introduce virtual threads to the Java Platform. Virtual threads are lightweight threads that dramatically reduce the effort of writing, maintaining, and observing high-throughput concurrent applications. This was a preview feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 19 (JEP 425) and reaching its second preview in OpenJDK 20 (JEP 436). It became final with OpenJDK 21 (JEP 444). Structured Concurrency ====================== https://openjdk.org/jeps/428 https://openjdk.org/jeps/437 https://openjdk.org/jeps/453 Simplify multithreaded programming by introducing an API for structured concurrency. Structured concurrency treats multiple tasks running in different threads as a single unit of work, thereby streamlining error handling and cancellation, improving reliability, and enhancing observability. This API is now a preview feature (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 453). It was first introduced in incubation (https://openjdk.java.net/jeps/11) in OpenJDK 19 (JEP 428) and had a second round of incubation in OpenJDK 20 (JEP 437). Scoped Values ============= https://openjdk.org/jeps/429 Introduce scoped values, which enable the sharing of immutable data within and across threads. They are preferred to thread-local variables, especially when using large numbers of virtual threads. This API is now a preview feature (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 429). It was first introduced in incubation (https://openjdk.java.net/jeps/11) in OpenJDK 20 (JEP 429). Sequenced Collections ===================== https://openjdk.org/jeps/431 Introduce new interfaces to represent collections with a defined encounter order. Each such collection has a well-defined first element, second element, and so forth, up to the last element. It also provides uniform APIs for accessing its first and last elements, and for processing its elements in reverse order. Key Encapsulation Mechanism API =============================== https://openjdk.org/jeps/452 Introduce an API for key encapsulation mechanisms (KEMs), an encryption technique for securing symmetric keys using public key cryptography. Virtual Machine Enhancements ============================ Generational ZGC ================ https://openjdk.org/jeps/439 Improve application performance by extending the Z Garbage Collector (ZGC) to maintain separate generations for young and old objects. This will allow ZGC to collect young objects — which tend to die young — more frequently. DEPRECATIONS ============ Deprecate the Windows 32-bit x86 Port for Removal ================================================= https://openjdk.org/jeps/449 Deprecate the Windows 32-bit x86 port, with the intent to remove it in a future release. Prepare to Disallow the Dynamic Loading of Agents ================================================= https://openjdk.org/jeps/451 Issue warnings when agents are loaded dynamically into a running JVM. These warnings aim to prepare users for a future release which disallows the dynamic loading of agents by default in order to improve integrity by default. Serviceability tools that load agents at startup will not cause warnings to be issued in any release.