234 lines
8.3 KiB
Plaintext
234 lines
8.3 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 21.0.0 (2023-09-XX):
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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 21.
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The full list of changes in 21u can be found at:
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- * https://builds.shipilev.net/backports-monitor/release-notes-21.txt
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NEW FEATURES
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============
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Language Features
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=================
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Pattern Matching for switch
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===========================
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https://openjdk.org/jeps/406
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https://openjdk.org/jeps/420
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https://openjdk.org/jeps/427
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https://openjdk.org/jeps/433
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https://openjdk.org/jeps/441
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Enhance the Java programming language with pattern matching for
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`switch` expressions and statements, along with extensions to the
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language of patterns. Extending pattern matching to `switch` allows an
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expression to be tested against a number of patterns, each with a
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specific action, so that complex data-oriented queries can be
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expressed concisely and safely.
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This was a preview feature (http://openjdk.java.net/jeps/12)
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introduced in OpenJDK 17 (JEP 406), which saw a second preview in
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OpenJDK 18 (JEP 420), a third in OpenJDK 19 (JEP 427) and a fourth
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(JEP 427) in OpenJDK 20. It became final with OpenJDK 21 (JEP 441).
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Record Patterns
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===============
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https://openjdk.org/jeps/405
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https://openjdk.org/jeps/432
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https://openjdk.org/jeps/440
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Enhance the Java programming language with record patterns to
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deconstruct record values. Record patterns and type patterns can be
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nested to enable a powerful, declarative, and composable form of data
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navigation and processing.
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This was a preview feature (http://openjdk.java.net/jeps/12) introduced
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in OpenJDK 19 (JEP 405) with a second preview (JEP 432) in OpenJDK 20.
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It became final with OpenJDK 21 (JEP 440).
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String Templates
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================
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https://openjdk.org/jeps/430
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Enhance the Java programming language with string templates. String
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templates complement Java's existing string literals and text blocks
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by coupling literal text with embedded expressions and template
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processors to produce specialized results.
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This is a preview feature (http://openjdk.java.net/jeps/12) introduced
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in OpenJDK 21 (JEP 430).
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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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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 is a preview feature (http://openjdk.java.net/jeps/12) introduced
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in OpenJDK 21 (JEP 443).
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Unnamed Classes and Instance Main Methods
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=========================================
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https://openjdk.org/jeps/445
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Evolve the Java language so that students can write their first
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programs without needing to understand language features designed for
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large programs. Far from using a separate dialect of Java, students
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can write streamlined declarations for single-class programs and then
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seamlessly expand their programs to use more advanced features as
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their skills grow.
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This is a preview feature (http://openjdk.java.net/jeps/12) introduced
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in OpenJDK 21 (JEP 445).
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Library Features
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================
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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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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 and
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OpenJDK 21 a sixth (JEP 448).
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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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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 a preview feature (http://openjdk.java.net/jeps/12).
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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 in OpenJDK 19 (JEP 424) and a
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second in OpenJDK 20 (JEP 434). It reaches a third preview in OpenJDK
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21 (JEP 442).
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Virtual Threads
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===============
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https://openjdk.org/jeps/425
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https://openjdk.org/jeps/436
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https://openjdk.org/jeps/444
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Introduce virtual threads to the Java Platform. Virtual threads are
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lightweight threads that dramatically reduce the effort of writing,
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maintaining, and observing high-throughput concurrent applications.
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This was a preview feature (http://openjdk.java.net/jeps/12)
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introduced in OpenJDK 19 (JEP 425) and reaching its second preview in
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OpenJDK 20 (JEP 436). It became final with OpenJDK 21 (JEP 444).
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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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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 is now a preview feature (http://openjdk.java.net/jeps/12) in
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OpenJDK 21 (JEP 453). It 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).
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Scoped Values
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=============
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https://openjdk.org/jeps/429
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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 is now a preview feature (http://openjdk.java.net/jeps/12)
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in OpenJDK 21 (JEP 429). It was first introduced in incubation
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(https://openjdk.java.net/jeps/11) in OpenJDK 20 (JEP 429).
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Sequenced Collections
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=====================
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https://openjdk.org/jeps/431
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Introduce new interfaces to represent collections with a defined
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encounter order. Each such collection has a well-defined first
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element, second element, and so forth, up to the last element. It also
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provides uniform APIs for accessing its first and last elements, and
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for processing its elements in reverse order.
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Key Encapsulation Mechanism API
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===============================
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https://openjdk.org/jeps/452
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Introduce an API for key encapsulation mechanisms (KEMs), an
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encryption technique for securing symmetric keys using public key
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cryptography.
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Virtual Machine Enhancements
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============================
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Generational ZGC
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================
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https://openjdk.org/jeps/439
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Improve application performance by extending the Z Garbage Collector
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(ZGC) to maintain separate generations for young and old objects. This
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will allow ZGC to collect young objects — which tend to die young —
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more frequently.
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DEPRECATIONS
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============
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Deprecate the Windows 32-bit x86 Port for Removal
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=================================================
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https://openjdk.org/jeps/449
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Deprecate the Windows 32-bit x86 port, with the intent to remove it in
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a future release.
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Prepare to Disallow the Dynamic Loading of Agents
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=================================================
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https://openjdk.org/jeps/451
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Issue warnings when agents are loaded dynamically into a running
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JVM. These warnings aim to prepare users for a future release which
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disallows the dynamic loading of agents by default in order to improve
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integrity by default. Serviceability tools that load agents at startup
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will not cause warnings to be issued in any release.
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