491 lines
19 KiB
Plaintext
491 lines
19 KiB
Plaintext
Key:
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JDK-X - https://bugs.openjdk.java.net/browse/JDK-X
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CVE-XXXX-YYYY: https://cve.mitre.org/cgi-bin/cvename.cgi?name=XXXX-YYYY
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New in release OpenJDK 24.0.0 (2025-03-18):
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===========================================
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Major changes are listed below. Some changes may have been backported
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to earlier releases following their first appearance in OpenJDK 22
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through to 25.
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NEW FEATURES
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============
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Language Features
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=================
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Flexible Constructor Bodies
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============================
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https://openjdk.org/jeps/447
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https://openjdk.org/jeps/482
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https://openjdk.org/jeps/492
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In constructors in the Java programming language, allow statements to
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appear before an explicit constructor invocation, i.e., super(..) or
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this(..). The statements cannot reference the instance under
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construction, but they can initialize its fields. Initializing fields
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before invoking another constructor makes a class more reliable when
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methods are overridden.
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This was introduced as a preview language feature
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(http://openjdk.java.net/jeps/12) in OpenJDK 22 (JEP 447) under the
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name "Statements before super(...)". It reached a second preview in
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OpenJDK 23 (JEP 482) with the addition of allowing fields to be
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initialized before invoking another constructor. It reaches a third
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preview in OpenJDK 24 (JEP 492).
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Unnamed Patterns and Variables
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==============================
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https://openjdk.org/jeps/443
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https://openjdk.org/jeps/456
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Enhance the Java language with unnamed patterns, which match a record
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component without stating the component's name or type, and unnamed
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variables, which can be initialized but not used. Both are denoted by
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an underscore character, _.
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This feature is now final. It was a preview feature
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(http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 443).
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Primitive Types in Patterns, instanceof, and switch
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===================================================
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https://openjdk.org/jeps/455
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https://openjdk.org/jeps/488
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Enhance pattern matching by allowing primitive type patterns in all
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pattern contexts, and extend instanceof and switch to work with all
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primitive types.
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This is a preview language feature (http://openjdk.java.net/jeps/12)
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introduced in OpenJDK 23 (JEP 455) and having its second preview in
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OpenJDK 24 (JEP 488).
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Module Import Declarations
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==========================
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https://openjdk.org/jeps/476
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https://openjdk.org/jeps/494
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Enhance the Java programming language with the ability to succinctly
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import all of the packages exported by a module. This simplifies the
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reuse of modular libraries, but does not require the importing code to
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be in a module itself.
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This is a preview language feature (http://openjdk.java.net/jeps/12)
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introduced in OpenJDK 23 (JEP 476) and reaching a second preview in
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OpenJDK 24 (JEP 494).
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Library Features
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================
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Foreign Function & Memory API
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=============================
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https://openjdk.org/jeps/412
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https://openjdk.org/jeps/419
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https://openjdk.org/jeps/424
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https://openjdk.org/jeps/434
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https://openjdk.org/jeps/442
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https://openjdk.org/jeps/454
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Introduce an API by which Java programs can interoperate with code and
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data outside of the Java runtime. By efficiently invoking foreign
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functions (i.e., code outside the JVM), and by safely accessing
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foreign memory (i.e., memory not managed by the JVM), the API enables
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Java programs to call native libraries and process native data without
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the brittleness and danger of JNI.
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This API is now finalised. It was first introduced in incubation
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(https://openjdk.java.net/jeps/11) in OpenJDK 17 (JEP 412), and is an
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evolution of the Foreign Memory Access API (OpenJDK 14 through 16) and
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Foreign Linker API (OpenJDK 16) (see release notes for
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java-17-openjdk). OpenJDK 18 saw a second round of incubation (JEP
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419) before its inclusion as a preview feature
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(http://openjdk.java.net/jeps/12) in OpenJDK 19 (JEP 424). A second
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preview took place in OpenJDK 20 (JEP 434) and a third and final
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preview in OpenJDK 21 (JEP 442).
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Prepare to Restrict the Use of JNI
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==================================
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https://openjdk.org/jeps/472
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Issue warnings about uses of the Java Native Interface (JNI) and
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adjust the Foreign Function & Memory (FFM) API to issue warnings in a
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consistent manner. All such warnings aim to prepare developers for a
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future release that ensures integrity by default by uniformly
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restricting JNI and the FFM API. Application developers can avoid both
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current warnings and future restrictions by selectively enabling these
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interfaces where essential using the --enable-native-access
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command-line option.
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Class-File API
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==============
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https://openjdk.org/jeps/457
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https://openjdk.org/jeps/466
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https://openjdk.org/jeps/484
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Provide a standard API for parsing, generating, and transforming Java
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class files.
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This API is now finalised. It was introduced as a preview library
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feature (http://openjdk.java.net/jeps/12) in OpenJDK 22 (JEP 457) with
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a second preview in OpenJDK 23 (JEP 466).
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Vector API
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==========
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https://openjdk.org/jeps/338
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https://openjdk.org/jeps/414
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https://openjdk.org/jeps/417
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https://openjdk.org/jeps/426
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https://openjdk.org/jeps/438
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https://openjdk.org/jeps/448
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https://openjdk.org/jeps/460
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https://openjdk.org/jeps/469
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https://openjdk.org/jeps/489
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Introduce an API to express vector computations that reliably compile
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at runtime to optimal vector hardware instructions on supported CPU
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architectures and thus achieve superior performance to equivalent
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scalar computations.
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This is an incubation feature (https://openjdk.java.net/jeps/11)
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introduced in OpenJDK 16 (JEP 338). A second round of incubation took
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place in OpenJDK 17 (JEP 414), OpenJDK 18 (JEP 417) saw a third,
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OpenJDK 19 a fourth (JEP 426), OpenJDK 20 (JEP 438) a fifth, OpenJDK
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21 a sixth (JEP 448), OpenJDK 22 a seventh (JEP 460), OpenJDK 23 an
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eighth (JEP 469) and it reaches its ninth in OpenJDK 24 (JEP 489).
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Stream Gatherers
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================
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https://openjdk.org/jeps/461
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https://openjdk.org/jeps/473
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https://openjdk.org/jeps/485
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Enhance the Stream API to support custom intermediate operations. This
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will allow stream pipelines to transform data in ways that are not
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easily achievable with the existing built-in intermediate operations.
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This API is now finalised. It was introduced as a preview library
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feature (http://openjdk.java.net/jeps/12) in OpenJDK 22 (JEP 461) with
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a second preview in OpenJDK 23 (JEP 473).
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Structured Concurrency
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======================
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https://openjdk.org/jeps/428
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https://openjdk.org/jeps/437
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https://openjdk.org/jeps/453
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https://openjdk.org/jeps/462
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https://openjdk.org/jeps/480
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https://openjdk.org/jeps/499
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Simplify multithreaded programming by introducing an API for
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structured concurrency. Structured concurrency treats multiple tasks
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running in different threads as a single unit of work, thereby
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streamlining error handling and cancellation, improving reliability,
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and enhancing observability.
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This API was first introduced in incubation
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(https://openjdk.java.net/jeps/11) in OpenJDK 19 (JEP 428) and had a
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second round of incubation in OpenJDK 20 (JEP 437). It became a
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preview feature (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP
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453), reached its second preview in OpenJDK 22 (JEP 462), had a third
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preview in OpenJDK 23 (JEP 480) and reaches its fourth in OpenJDK 24
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(JEP 499).
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Simple Source Files and Instance Main Methods
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=============================================
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https://openjdk.org/jeps/445
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https://openjdk.org/jeps/463
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https://openjdk.org/jeps/477
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https://openjdk.org/jeps/495
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Evolve the Java programming language so that beginners can write their
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first programs without needing to understand language features
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designed for large programs. Far from using a separate dialect of the
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language, beginners can write streamlined declarations for
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single-class programs and then seamlessly expand their programs to use
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more advanced features as their skills grow. Experienced developers
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can likewise enjoy writing small programs succinctly, without the need
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for constructs intended for programming in the large.
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This library feature was introduced as a preview
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(http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP 445) under the
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name "Unnamed Classes and Instance Main Methods". It reached a second
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preview in OpenJDK 22 (JEP 463) and a third in OpenJDK 23 (JEP 477)
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under the new name, "Implicitly Declared Classes and Instance Main
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Methods", due to the move away from unnamed classes to an implicitly
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declared name chosen by the host system. It has a fourth preview in
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OpenJDK 24 (JEP 495) with new terminology and a revised title, but
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otherwise unchanged.
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Scoped Values
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=============
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https://openjdk.org/jeps/429
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https://openjdk.org/jeps/446
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https://openjdk.org/jeps/464
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https://openjdk.org/jeps/481
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https://openjdk.org/jeps/487
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Introduce scoped values, which enable the sharing of immutable data
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within and across threads. They are preferred to thread-local
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variables, especially when using large numbers of virtual threads.
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This API was first introduced in incubation
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(https://openjdk.java.net/jeps/11) in OpenJDK 20 (JEP 429). It became
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a preview feature (http://openjdk.java.net/jeps/12) in OpenJDK 21 (JEP
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446), had a second preview in OpenJDK 22 (JEP 464), a third in OpenJDK
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23 (JEP 481) and reaches its fourth in OpenJDK 24 (JEP 487).
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Key Derivation Function API
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===========================
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https://openjdk.org/jeps/478
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Introduce an API for Key Derivation Functions (KDFs), which are
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cryptographic algorithms for deriving additional keys from a secret
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key and other data.
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This is a preview library feature (http://openjdk.java.net/jeps/12)
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introduced in OpenJDK 24 (JEP 478).
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Quantum-Resistant Module-Lattice-Based Key Encapsulation Mechanism
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==================================================================
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https://openjdk.org/jeps/496
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Enhance the security of Java applications by providing an
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implementation of the quantum-resistant Module-Lattice-Based
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Key-Encapsulation Mechanism (ML-KEM). Key encapsulation mechanisms
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(KEMs) are used to secure symmetric keys over insecure communication
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channels using public key cryptography. ML-KEM is designed to be
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secure against future quantum computing attacks. It has been
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standardized by the United States National Institute of Standards and
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Technology (NIST) in FIPS 203 [0].
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[0] https://csrc.nist.gov/pubs/fips/203/final
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Quantum-Resistant Module-Lattice-Based Digital Signature Algorithm
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==================================================================
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https://openjdk.org/jeps/497
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Enhance the security of Java applications by providing an
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implementation of the quantum-resistant Module-Lattice-Based Digital
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Signature Algorithm (ML-DSA). Digital signatures are used to detect
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unauthorized modifications to data and to authenticate the identity of
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signatories. ML-DSA is designed to be secure against future quantum
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computing attacks. It has been standardized by the United States
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National Institute of Standards and Technology (NIST) in FIPS 204 [0].
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[0] https://csrc.nist.gov/pubs/fips/204/final
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Virtual Machine Enhancements
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============================
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Region Pinning for G1
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=====================
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https://openjdk.org/jeps/423
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Reduce latency by implementing region pinning in G1, so that garbage
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collection need not be disabled during Java Native Interface (JNI)
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critical regions.
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ZGC: Generational Mode by Default
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=================================
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https://openjdk.org/jeps/439
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https://openjdk.org/jeps/474
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Switch the default mode of the Z Garbage Collector (ZGC) to the
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generational mode. Deprecate the non-generational mode, with the
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intent to remove it in a future release.
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Late Barrier Expansion for G1
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=============================
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https://openjdk.org/jeps/475
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Simplify the implementation of the G1 garbage collector's barriers,
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which record information about application memory accesses, by
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shifting their expansion from early in the C2 JIT's compilation
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pipeline to later.
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Ahead-of-Time Class Loading & Linking
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=====================================
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https://openjdk.org/jeps/483
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Improve startup time by making the classes of an application instantly
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available, in a loaded and linked state, when the HotSpot Java Virtual
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Machine starts. Achieve this by monitoring the application during one
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run and storing the loaded and linked forms of all classes in a cache
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for use in subsequent runs. Lay a foundation for future improvements
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to both startup and warmup time.
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Using this feature requires a three stage process:
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1. Populate the Ahead-of-Time configuration data with a training run
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of the application using the options `-XX:AOTMode=record
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-XX:AOTConfiguration=<config name>` where `<config name>` is the
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configuration reference to use in #2.
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2. Create the Ahead-of-Time cache using the options
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`-XX:AOTMode=create -XX:AOTConfiguration=<config name>
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-XX:AOTCache=<cache name>` where `<config name>` is the configuration
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reference from #1 and `<cache name>` is the cache reference to use in
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later runs.
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3. When running the application in testing or production, use the
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option `-XX:AOTCache=<cache name>` to run the application with the
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cache generated in #2.
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Synchronize Virtual Threads without Pinning
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===========================================
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https://openjdk.org/jeps/491
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Improve the scalability of Java code that uses synchronized methods
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and statements by arranging for virtual threads that block in such
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constructs to release their underlying platform threads for use by
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other virtual threads. This will eliminate nearly all cases of virtual
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threads being pinned to platform threads, which severely restricts the
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number of virtual threads available to handle an application's
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workload.
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Generational Shenandoah
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=======================
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https://openjdk.org/jeps/404
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Enhance the Shenandoah garbage collector with experimental
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generational collection capabilities to improve sustainable
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throughput, load-spike resilience, and memory utilization.
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This is an experimental feature that needs to be explicitly enabled
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with -XX:+UnlockExperimentalVMOptions
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-XX:ShenandoahGCMode=generational
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Compact Object Headers
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======================
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https://openjdk.org/jeps/450
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Reduce the size of object headers in the HotSpot JVM from between 96
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and 128 bits down to 64 bits on 64-bit architectures. This will reduce
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heap size, improve deployment density, and increase data locality.
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This is an experimental feature that needs to be explicitly enabled
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with -XX:+UnlockExperimentalVMOptions -XX:+UseCompactObjectHeaders
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Tools
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=====
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Launch Multi-File Source-Code Programs
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======================================
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https://openjdk.org/jeps/458
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Enhance the java application launcher to be able to run a program
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supplied as multiple files of Java source code. This will make the
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transition from small programs to larger ones more gradual, enabling
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developers to choose whether and when to go to the trouble of
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configuring a build tool.
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Markdown Documentation Comments
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===============================
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https://openjdk.org/jeps/467
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Enable JavaDoc documentation comments to be written in Markdown rather
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than solely in a mixture of HTML and JavaDoc @-tags.
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Linking Run-Time Images without JMODs
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=====================================
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https://openjdk.org/jeps/493
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Reduce the size of the JDK by approximately 25% by enabling the jlink
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tool to create custom run-time images without using the JDK's JMOD
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files.
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This feature must be enabled when the JDK is built using the
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--enable-linkable-runtime option. It will not be enabled by default,
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and some JDK vendors may choose not to enable it.
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DEPRECATIONS
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============
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Deprecate the Memory-Access Methods in sun.misc.Unsafe for Removal
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==================================================================
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https://openjdk.org/jeps/471
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Deprecate the memory-access methods in sun.misc.Unsafe for removal in
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a future release. These unsupported methods have been superseded by
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standard APIs, namely the VarHandle API (JEP 193, OpenJDK 9) and the
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Foreign Function & Memory API (JEP 454, OpenJDK 22). We strongly
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encourage library developers to migrate from sun.misc.Unsafe to
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supported replacements, so that applications can migrate smoothly to
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modern JDK releases.
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Warn upon Use of Memory-Access Methods in sun.misc.Unsafe
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=========================================================
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https://openjdk.org/jeps/498
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Issue a warning at run time on the first occasion that any
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memory-access method in sun.misc.Unsafe is invoked. All of these
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unsupported methods were terminally deprecated in JDK 23 (see JEP 471
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above). They have been superseded by standard APIs, namely the
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VarHandle API (JEP 193, OpenJDK 9) and the Foreign Function & Memory
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API (JEP 454, OpenJDK 22). We strongly encourage library developers to
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migrate from sun.misc.Unsafe to supported replacements, so that
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applications can migrate smoothly to modern JDK releases.
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Permanently Disable the Security Manager
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========================================
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https://openjdk.org/jeps/486
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The Security Manager has not been the primary means of securing
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client-side Java code for many years, it has rarely been used to
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secure server-side code, and it is costly to maintain. We therefore
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deprecated it for removal in OpenJDK 17 via JEP 411 (2021). As the
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next step toward removing the Security Manager, we will revise the
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Java Platform specification so that developers cannot enable it and
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other Platform classes do not refer to it. This change will have no
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impact on the vast majority of applications, libraries, and tools. We
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will remove the Security Manager API in a future release.
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Deprecate the 32-bit x86 Port for Removal
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=========================================
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https://openjdk.org/jeps/501
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Deprecate the 32-bit x86 port, with the intent to remove it in a
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future release. This will thereby deprecate the Linux 32-bit x86 port,
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which is the only 32-bit x86 port remaining in the JDK. It will also,
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effectively, deprecate any remaining downstream 32-bit x86
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ports. After the 32-bit x86 port is removed, the architecture-agnostic
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Zero port will be the only way to run Java programs on 32-bit x86
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processors.
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REMOVALS
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========
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String Templates
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================
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https://openjdk.org/jeps/430
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https://openjdk.org/jeps/459
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https://openjdk.org/jeps/465
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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
|
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OpenJDK 23 (JEP 465) and the feature is no longer present. See [0]
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for further explanation.
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[0] https://mail.openjdk.org/pipermail/amber-spec-experts/2024-April/004106.html
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Remove the Windows 32-bit x86 Port
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==================================
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https://openjdk.org/jeps/449
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https://openjdk.org/jeps/479
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Remove the source code and build support for the Windows 32-bit x86
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port. This port was deprecated for removal in JDK 21 by JEP 449 with
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the express intent to remove it in a future release.
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ZGC: Remove the Non-Generational Mode
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=====================================
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https://openjdk.org/jeps/439
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https://openjdk.org/jeps/474
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https://openjdk.org/jeps/490
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Remove the non-generational mode of the Z Garbage Collector (ZGC),
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keeping the generational mode as the default for ZGC (see JEP 439 &
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474).
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