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 23.0.0 (2024-09-17): =========================================== Major changes are listed below. Some changes may have been backported to earlier releases following their first appearance in OpenJDK 22 through to 25. NEW FEATURES ============ Language Features ================= Flexible Constructor Bodies ============================ https://openjdk.org/jeps/447 https://openjdk.org/jeps/482 In constructors in the Java programming language, allow statements to appear before an explicit constructor invocation, i.e., super(..) or this(..). The statements cannot reference the instance under construction, but they can initialize its fields. Initializing fields before invoking another constructor makes a class more reliable when methods are overridden. This was introduced as a preview language feature (http://openjdk.java.net/jeps/12) in OpenJDK 22 (JEP 447) under the name "Statements before super(...)". It reaches a second preview in OpenJDK 23 (JEP 482) with the addition of allowing fields to be initialized before invoking another constructor. Unnamed Patterns and Variables ============================== https://openjdk.org/jeps/443 https://openjdk.org/jeps/456 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 feature is now final. It was a preview feature (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 443). Primitive Types in Patterns, instanceof, and switch =================================================== https://openjdk.org/jeps/455 Enhance pattern matching by allowing primitive type patterns in all pattern contexts, and extend instanceof and switch to work with all primitive types. This is a preview language feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 23 (JEP 455). Module Import Declarations ========================== https://openjdk.org/jeps/476 Enhance the Java programming language with the ability to succinctly import all of the packages exported by a module. This simplifies the reuse of modular libraries, but does not require the importing code to be in a module itself. This is a preview language feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 23 (JEP 476). Library Features ================ 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 https://openjdk.org/jeps/454 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 finalised. 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 feature (http://openjdk.java.net/jeps/12) in OpenJDK 19 (JEP 424). A second preview took place in OpenJDK 20 (JEP 434) and a third and final preview in OpenJDK 21 (JEP 442). Class-File API ============== https://openjdk.org/jeps/457 https://openjdk.org/jeps/466 Provide a standard API for parsing, generating, and transforming Java class files. This is a preview library feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 22 (JEP 457) with a second preview in OpenJDK 23 (JEP 466). 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 https://openjdk.org/jeps/460 https://openjdk.org/jeps/469 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, OpenJDK 21 a sixth (JEP 448), OpenJDK 22 a seventh (JEP 460) and it reaches its eighth in OpenJDK 23 (JEP 469). Stream Gatherers ================ https://openjdk.org/jeps/461 https://openjdk.org/jeps/473 Enhance the Stream API to support custom intermediate operations. This will allow stream pipelines to transform data in ways that are not easily achievable with the existing built-in intermediate operations. This is a preview library feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 22 (JEP 461) with a second preview in OpenJDK 23 (JEP 473). Structured Concurrency ====================== https://openjdk.org/jeps/428 https://openjdk.org/jeps/437 https://openjdk.org/jeps/453 https://openjdk.org/jeps/462 https://openjdk.org/jeps/480 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 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). It became a preview feature (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 453), reached its second preview in OpenJDK 22 (JEP 462) and has a third preview in OpenJDK 23 (JEP 480). Implicitly Declared Classes and Instance Main Methods ===================================================== https://openjdk.org/jeps/445 https://openjdk.org/jeps/463 https://openjdk.org/jeps/477 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 library feature was introduced as a preview (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 445) under the name "Unnamed Classes and Instance Main Methods". It reaches a second preview in OpenJDK 22 (JEP 463) and a third in OpenJDK 23 (JEP 477) under a new name, due to the move away from unnamed classes to an implicitly declared name chosen by the host system. Scoped Values ============= https://openjdk.org/jeps/429 https://openjdk.org/jeps/446 https://openjdk.org/jeps/464 https://openjdk.org/jeps/481 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 was first introduced in incubation (https://openjdk.java.net/jeps/11) in OpenJDK 20 (JEP 429). It became a preview feature (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 446), reached its second preview in OpenJDK 22 (JEP 464) and a third in OpenJDK 23 (JEP 481). Virtual Machine Enhancements ============================ Region Pinning for G1 ===================== https://openjdk.org/jeps/423 Reduce latency by implementing region pinning in G1, so that garbage collection need not be disabled during Java Native Interface (JNI) critical regions. ZGC: Generational Mode by Default ================================= https://openjdk.org/jeps/474 Switch the default mode of the Z Garbage Collector (ZGC) to the generational mode. Deprecate the non-generational mode, with the intent to remove it in a future release. Tools ===== Launch Multi-File Source-Code Programs ====================================== https://openjdk.org/jeps/458 Enhance the java application launcher to be able to run a program supplied as multiple files of Java source code. This will make the transition from small programs to larger ones more gradual, enabling developers to choose whether and when to go to the trouble of configuring a build tool. Markdown Documentation Comments =============================== https://openjdk.org/jeps/467 Enable JavaDoc documentation comments to be written in Markdown rather than solely in a mixture of HTML and JavaDoc @-tags. DEPRECATIONS ============ Deprecate the Memory-Access Methods in sun.misc.Unsafe for Removal ================================================================== https://openjdk.org/jeps/471 Deprecate the memory-access methods in sun.misc.Unsafe for removal in a future release. These unsupported methods have been superseded by standard APIs, namely the VarHandle API (JEP 193, OpenJDK 9) and the Foreign Function & Memory API (JEP 454, OpenJDK 22). We strongly encourage library developers to migrate from sun.misc.Unsafe to supported replacements, so that applications can migrate smoothly to modern JDK releases. REMOVALS ======== String Templates ================ https://openjdk.org/jeps/430 https://openjdk.org/jeps/459 https://openjdk.org/jeps/465 This was a preview feature (http://openjdk.java.net/jeps/12) introduced in OpenJDK 21 (JEP 430) with a second preview in OpenJDK 22 (JEP 459). A third preview was proposed but ultimately withdrawn for OpenJDK 23 (JEP 465) and the feature is no longer present. See [0] for further explanation. [0] https://mail.openjdk.org/pipermail/amber-spec-experts/2024-April/004106.html