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SeeJDK 23 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 23.

The following are some of the updates in Java SE 23 and JDK 23:

Language Preview Features

• Pattern matching is now enhanced by allowing primitive type patterns in all pattern contexts. Theinstanceof andswitch operators, expressions, and statements work with all primitive types.

  SeeJEP 455: Primitive Types in Patterns, instanceof, and switch (Preview) and the following sections inJava Platform, Standard Edition Java Language Updates:

  • When Clauses
  • Type Patterns with Primitive Types
  • Primitive Types in Record Patterns
  • Primitive Values in switch Expressions and Statements
  • Safe casting with instanceof and switch
• Module Import Declarations enable you to succinctly import all of the packages exported by a module with a module import declaration. It simplifies the reuse of modular libraries without requiring the imported code to be in a module.

  SeeJEP 476: Module Import Declarations (Preview) andModule Import Declarations inJava Platform, Standard Edition Java Language Updates.

• Flexible Constructor Bodies enable you to add statements that don't reference the instance being created before an explicit constructor invocation. This feature helps you to prepare arguments for a superclass constructor by performing nontrivial computations or to validate arguments you want to pass to a superclass constructor.

  SeeJEP 482: Flexible Constructor Bodies (Second Preview) andFlexible Constructor Bodies inJava Platform, Standard Edition Java Language Updates.

• Implicitly Declared Classes and Instance Main Methods enable students to write their first programs even without learning the full set of language features designed for large programs. Students can write streamlined declarations for single-class programs and then seamlessly expand their programs to use more advanced features as their skills grow.

  SeeJEP 477: Implicitly Declared Classes and Instance Main Methods (Third Preview) andImplicitly Declared Classes and Instance Main Methods inJava Platform, Standard Edition Java Language Updates.

• String Templates were first previewed in JDK 21 (JEP 430) and in JDK 22 (JEP 459). String templates were intended to be re-previewed in JDK 23 (JEP 465). However, after extensive feedback and discussion, we concluded that the feature is unsuitable in its current form. There is no consensus on what a better design will be; therefore, we have withdrawn the feature for now, and JDK 23 will not include it.

  SeeMarch 2024 Archives by thread andUpdate on String Templates (JEP 459) from the Project Amber amber-spec-experts mailing list for further discussion.

SeeJEP 12: Preview Features andPreview Language and VM Features inJava Platform, Standard Edition Java Language Updates.

Library Improvements Previews and Incubator

• The Class-File API is used for parsing, generating, and transforming Java class files.

  SeeJEP 466: Class-File API (Second Preview) andClass-File API inJava Platform, Standard Edition Java Virtual Machine Guide.

• Stream gatherers enable you to create custom intermediate operations, which allow stream pipelines to transform data in ways that aren't easily achievable with existing built-in intermediate operations.

  SeeJEP 473: Stream Gatherers (Second Preview) andStream Gatherers inJava Platform, Standard Edition Core Libraries.

• 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.

  SeeJEP 480: Structured Concurrency (Third Preview) andStructured Concurrency inJava Platform, Standard Edition Core Libraries.

• Scoped values enables sharing of immutable data within and across threads. They are preferred to thread-local variables, especially when using large numbers of virtual threads.

  SeeJEP 481: Scoped Values (Third Preview) and theScopedValue class in the Java API Specification.

• The Vector API is introduced to express vector computations that reliably compile at runtime to optimal vector instructions on supported CPU architectures, thus achieving performance superior to equivalent scalar computations. SeeJEP 469: Vector API (Eighth Incubator).

SeeJEP 11: Incubator Modules.

Runtime Improvements

• The ZGC garbage collector now runs in the generational mode by default. The non-generational mode of ZGC has been deprecated for removal. This will generally improve application performance, although a small number of workloads that are non-generational in nature may be impacted negatively.

  SeeJEP 474: ZGC: Generational Mode by Default and the sectionThe Z Garbage Collector inJava Platform, Standard Edition HotSpot Virtual Machine Garbage Collection Tuning Guide.

• The Oracle GraalVM JIT compiler (Graal JIT) is now included among the JITs available as part of the Oracle JDK. This integration offers innovations previously made available throughOracle GraalVM, such as novel JIT code optimization techniques (seeCompiler Advantages in the GraalVM documentation). This provides developers and system administrators more options to help fine tune and improve peak performance of their applications. The Graal JIT is enabled by passing the command line options to the Java executable:

  -XX:+UnlockExperimentalVMOptions -XX:+UseGraalJIT

  If you do not pass these flags at JVM startup, the Oracle JDK default JIT (C2) will run as usual.

Tooling

JavaDoc documentation comments can now be written in Markdown syntax along with HTML elements and JavaDoc tags.

SeeJEP 467: Markdown Documentation Comments andMarkdown in Documentation Comments inJava Platform, Standard Edition JavaDoc Guide.

Removed APIs, Tools, and Components

For more details on removals and deprecations, seeFeatures and Options Removed and Deprecated in JDK 23.

In addition, there are security related updates that you need to be aware of. SeeSecurity Updates in JDK 23.

SeeJDK 22 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 22.

The following are some of the updates in Java SE 22 and JDK 22:

Language Features

• Unnamed variables and unnamed patterns can be used when variable declarations or nested patterns are required but never used. Unnamed patterns can appear in a pattern list of a record pattern and can be used instead of a type pattern. You denote both with the underscore character(_).

  SeeJEP 456: Unnamed Variables & Patterns andUnnamed Variables and Patterns inJava Platform, Standard Edition Java Language Updates.

Preview Language Features

• In constructors, you can add statements that don't reference the instance being created before an explicit constructor invocation. You can use this feature to prepare arguments for a superclass constructor by performing nontrivial computations or validate arguments you want to pass to a superclass constructor.

  SeeJEP 447: Statements before super(...) andStatements Before super(...) inJava Platform, Standard Edition Java Language Updates.

• 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. Embedded expressions are Java expressions with additional syntax that differentiates them from the literal text in the string template. A template processor combines the literal text in the template with the values of the embedded expressions to produce a result.

  SeeJEP 459: String Templates (Second Preview) andString Templates inJava Platform, Standard Edition Java Language Updates.

• The preview features Instance Main Methods and Implicitly Declared Classes enable students to write their first programs without needing to understand the full set of language features designed for large programs. They can write streamlined declarations for single-class programs and then seamlessly expand their programs to use more advanced features as their skills grow.

  SeeJEP 463: Implicitly Declared Classes and Instance Main Methods (Second Preview) andImplicitly Declared Classes and Instance Main Methods inJava Platform, Standard Edition Java Language Updates.

SeePreview Language and VM Features for more information about preview features.

Library Improvements

• The Foreign Function and Memory (FFM) API enables Java programs to interoperate with code and data outside the Java runtime. This API enables Java programs to call native libraries and process native data without the brittleness and danger of JNI. The API invokes foreign functions, code outside the JVM, and safely accesses foreign memory, memory not managed by the JVM.

  SeeJEP 454: Foreign Function & Memory API andForeign Function and Memory API inJava Platform, Standard Edition Core Libraries.

Library Improvements Previews and Incubator

• Stream gatherers enable you to create custom intermediate operations, which allow stream pipelines to transform data in ways that aren't easily achievable with existing built-in intermediate operations.

  SeeJEP 461: Stream Gatherers (Preview) andStream Gatherers inJava Platform, Standard Edition Core Libraries.

• The Class-File API is used for parsing, generating, and transforming Java class files.

  SeeJEP 457: Class-File API (Preview) andClass-File API inJava Platform, Standard Edition Java Virtual Machine Guide.

• 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.

  SeeJEP 462: Structured Concurrency (Second Preview) andStructured Concurrency inJava Platform, Standard Edition Core Libraries.

• Scoped values enables sharing of immutable data within and across threads. They are preferred to thread-local variables, especially when using large numbers of virtual threads.

  SeeJEP 464: Scoped Values (Second Preview) and theScopedValue class in the Java API Specification.

• The Vector API is introduced to express vector computations that reliably compile at runtime to optimal vector instructions on supported CPU architectures, thus achieving performance superior to equivalent scalar computations. SeeJEP 460: Vector API (Seventh Incubator).

SeeJEP 12: Preview Features andJEP 11: Incubator Modules for more information about preview features and incubating APIs.

Performance Improvements

Region pinning in G1 reduces latency so that garbage collection need not be disabled during Java Native Interface (JNI) critical regions.

SeeJEP 423: Region Pinning for G1 and the sectionEvacuation Failure inJava Platform, Standard Edition HotSpot Virtual Machine Garbage Collection Tuning Guide.

Tooling

The Java application launcher is enhanced to run a program supplied as multiple files of Java source code. This will enable gradual transition from small programs to larger ones.

SeeJEP 458: Launch Multi-File Source-Code Programs.

Removed APIs, Tools, and Components

For more details on removals and deprecations, seeFeatures and Options Removed and Deprecated in JDK 22.

In addition, there are security related updates that you need to be aware of. SeeSecurity Updates in JDK 22.

SeeJDK 21 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 21.

The following are some of the updates in Java SE 21 and JDK 21:

Language Features

• Record patterns and type patterns can be nested to enable a powerful, declarative, and composable form of data navigation and processing. You can use a record pattern to test whether a value is an instance of a record class type and, if it is, to recursively perform pattern matching on its component values. In this release, support for record patterns appearing in the header of an enhancedfor statement has been removed.

  SeeJEP 440: Record Patterns andRecord Patterns inJava Platform, Standard Edition Java Language Updates.

• Aswitch statement transfers control to one of several statements or expressions, depending on the value of its selector expression. Extending pattern matching toswitch 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. In this release:
  • Parenthesized patterns have been removed.
  • Qualifiedenum constants ascase constants inswitch expressions and statements are allowed.

  SeeJEP 441: Pattern Matching for switch andPattern Matching for switch Expressions and Statements inJava Platform, Standard Edition Java Language Updates.

Preview Language Features

• 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.

  SeeJEP 430: String Templates (Preview) andString Templates inJava Platform, Standard Edition Java Language Updates.

• Unnamed patterns match a record component without stating the component's name or type. Unnamed variables are variables that can be initialized but not used. You denote both with the underscore character (_).

  SeeJEP 443: Unnamed Patterns and Variables (Preview) andUnnamed Patterns and Variables inJava Platform, Standard Edition Java Language Updates.

• Unnamed classes and instance main methods enable students to write streamlined declarations for single-class programs and then seamlessly expand their programs later to use more advanced features as their skills grow.

  SeeJEP 445: Unnamed Classes and Instance Main Methods (Preview) andUnnamed Classes and Instance Main Methods inJava Platform, Standard Edition Java Language Updates.

SeePreview Language and VM Features for more information about preview features.

Library Improvements

• Virtual threads are lightweight threads that reduce the effort of writing, maintaining, and debugging high-throughput concurrent applications.

  SeeJEP 444: Virtual Threads andVirtual Threads inJava Platform, Standard Edition Core Libraries.

• Sequenced collections are 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 is an interface that represents a sequenced collection, provides uniform APIs for accessing its first and last elements, and for processing its elements in reverse order.

  SeeJEP 431: Sequenced Collections andCreating Sequenced Collections, Sets, and Maps inJava Platform, Standard Edition Core Libraries.

• The Key Encapsulation Mechanism API is introduced for key encapsulation mechanisms (KEMs), an encryption technique for securing symmetric keys using public key cryptography.

  SeeJEP 452: Key Encapsulation Mechanism API andThe KEM Class inJava Platform, Standard Edition Security Developer's Guide.

Library Improvements Previews and Incubator

• The preview API Foreign Function and Memory API has been further refined as follows:
  • Centralized the management of the lifetimes of native segments in theArena interface
  • Enhanced layout paths with a new element to dereference address layouts
  • Provided a linker option to optimize calls to functions that are short-lived and will not upcall to Java (e.g.,clock_gettime)
  • Provided a fallback native linker implementation, based onlibffi, to facilitate porting
  • Removed theVaList class
  SeeJEP 442: Foreign Function & Memory API (Third Preview) andForeign Function and Memory API inJava Platform, Standard Edition Core Libraries.
• 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.

  SeeJEP 453: Structured Concurrency (Preview) andStructured Concurrency inJava Platform, Standard Edition Core Libraries.

• Scoped values enables sharing of immutable data within and across threads. They are preferred to thread-local variables, especially when using large numbers of virtual threads.

  SeeJEP 446: Scoped Values (Preview) and theScopedValue class in the Java API Specification.

• The Vector API is introduced to express vector computations that reliably compile at runtime to optimal vector instructions on supported CPU architectures, thus achieving performance superior to equivalent scalar computations. SeeJEP 448: Vector API (Sixth Incubator).

SeeJEP 12: Preview Features andJEP 11: Incubator Modules for more information about preview features and incubating APIs.

Performance Improvements

Application performance has been improved by extending the Z Garbage Collector (ZGC) to maintain separategenerations for young and old objects. This will allow ZGC to collect young objects, which tend to die young, more frequently.

SeeJEP 439: Generational ZGC andThe Z Garbage Collector inJava Platform, Standard Edition HotSpot Virtual Machine Garbage Collection Tuning Guide.

Stewardship

Warnings are issued 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.

SeeJEP 451: Prepare to Disallow the Dynamic Loading of Agents.

Removed APIs, Tools, and Components

For more details on removals and deprecations, seeFeatures and Options Removed and Deprecated in JDK 21.

In addition, there are security related updates that you need to be aware of. SeeSecurity Updates in JDK 21.

SeeJDK 20 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 20.

The following are some of the updates in Java SE 20 and JDK 20:

Concurrency Model Previews and Incubators

• Virtual threads are lightweight threads that reduce the effort of writing, maintaining, and debugging high-throughput concurrent applications. This is a preview API. Minor changes have been made to this API since the last release. SeeJEP 436: Virtual Threads (Second Preview) andVirtual Threads inJava Platform, Standard Edition Core Libraries.
• 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. SeeJEP 437: Structured Concurrency (Second Incubator). SeeJEP 11: Incubator Modules for more information about incubating APIs.
• Scoped values enables sharing of immutable data within and across threads. They are preferred to thread-local variables, especially when using large numbers of virtual threads. SeeJEP 429: Scoped Values (Incubator) andJEP 11: Incubator Modules.
• An API is introduced to express vector computations that reliably compile at runtime to optimal vector instructions on supported CPU architectures, thus achieving performance superior to equivalent scalar computations. SeeJEP 438: Vector API (Fifth Incubator).

Language Changes

• The preview feature Pattern Matching forswitch Expressions and Statements has been further refined as follows:
  • An exhaustive switch (that is, aswitch expression or a patternswitch statement) over anenum class throws aMatchException instead of an IncompatibleClassChangeError if noswitch label applies at run time.
  • The grammar forswitch labels is simpler.
  • The compiler can infer the type of the type arguments for generic record patterns in all constructs that accept patterns:switch statements and expressions,instanceof expressions, and enhancedfor statements.
  SeeJEP 433: Pattern Matching for switch (Fourth Preview) andPattern Matching for switch Expressions and Statements inJava Platform, Standard Edition Java Language Updates.
• The preview feature Record Patterns has been further refined as follows:
  • The compiler can infer the type of the type arguments for generic record patterns.
  • Record patterns can appear in an enhancedfor statement.
  • Named record patterns are no longer supported.
  SeeJEP 432: Record Patterns (Second Preview) andRecord Patterns inJava Platform, Standard Edition Java Language Updates.

SeePreview Language and VM Features for more information about preview features.

Library Changes

• The preview API Foreign Function and Memory API has been further refined as follows:
  • TheMemorySegment andMemoryAddress abstractions are unified (memory addresses are now modeled by zero-length memory segments).
  • The sealedMemoryLayout hierarchy is enhanced to facilitate usage with pattern matching in switch expressions and statements. SeePattern Matching for switch Expressions and Statements.
  • MemorySession has been split into Arena andSegmentScope to facilitate sharing segments across maintenance boundaries
  SeeJEP 434: Foreign Function & Memory API (Second Preview) andForeign Function and Memory API inJava Platform, Standard Edition Core Libraries.

Removed APIs, Tools, and Components

For more details on removals and deprecations, seeFeatures and Options Deprecated in JDK 20.

In addition, there are security related updates that you need to be aware of. SeeSecurity Updates in JDK 20.

SeeJDK 19 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 19.

The following are some of the updates in Java SE 19 and JDK 19:

Concurrency Model Update Previews

• Virtual threads are lightweight threads that reduce the effort of writing, maintaining, and debugging high-throughput concurrent applications. This is apreview API. SeeJEP 425: Virtual Threads (Preview) andVirtual Threads inJava Platform, Standard Edition Core Libraries.
• An API is introduced to simplify multithreaded programming 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. SeeJEP 428: Structured Concurrency (Incubator).

Language Changes

• Record Patterns is introduced as a preview feature for this release. A record pattern consists of a type, a record component pattern list used to match against the corresponding record components, and an optional identifier. You can nest record patterns and type patterns to enable a powerful, declarative, and composable form of data navigation and processing. SeeJEP 405: Record Patterns (Preview) andRecord Patterns inJava Platform, Standard Edition Java Language Updates.
• The preview feature Pattern Matching forswitch Expressions and Statements has been re-previewed in this release. This feature enables 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. SeeJEP 427: Pattern Matching for switch (Third Preview) andPattern Matching for switch Expressions and Statements inJava Platform, Standard Edition Java Language Updates.

Library Changes

• The Foreign Function and Memory API enables Java programs to interoperate with code and data outside the Java runtime. This API enables Java programs to call native libraries and process native data without the brittleness and danger of JNI. The API invokes foreign functions, code outside the JVM, and safely accesses foreign memory that is not managed by the JVM. This is apreview API. SeeJEP 424: Foreign Function & Memory API (Preview) andForeign Function and Memory API inJava Platform, Standard Edition Core Libraries.
• The Vector API is introduced to express vector computations that reliably compile at runtime to optimal vector instructions on supported CPU architectures, thus achieving performance superior to equivalent scalar computations. SeeJEP 426: Vector API (Fourth Incubator).

Removed APIs, Tools, and Components

For more details on removals and deprecations, seeFeatures and Options Deprecated in JDK 19.

In addition, there are security related updates that you need to be aware of. SeeSecurity Updates in JDK 19.

SeeJDK 18 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 18.

The following are some of the updates in Java SE 18 and JDK 18:

Tools

• The new command-line tooljwebserver enables you to start a minimal web server that serves static files. This tool is useful for prototyping and testing. SeeJEP 408: Simple Web Server.
• A@snippet tag is added to JavaDoc's Standard Doclet, which simplifies the inclusion of example source code in API documentation. SeeJEP 413: Code Snippets in Java API Documentation andProgrammer's Guide to Snippets.

Library Changes

• UTF-8 is now the default charset for the Java SE APIs. With this change, APIs that depend on the default charset will behave consistently across all implementations, operating systems, locales, and configurations. SeeJEP 400: UTF-8 by Default andBe Aware Of The Default Charset.
• A service-provider interface (SPI) is defined for the host name and address resolution, so thatjava.net.InetAddress can make use of resolvers other than the platform's built-in resolver. SeeJEP 418: Internet-Address Resolution SPI. See also the sectionSpecify Mappings from Host Names to IP Addresses inJava Platform, Standard Edition Core Libraries for information about thejdk.net.hosts.file system property, which enables you to configureInetAddress to use a specifichosts file, rather than the system-wide resolver, to map host names to IP addresses.
• Core reflection with method handles has been reimplemented. This will reduce the maintenance and development cost of both thejava.lang.reflect andjava.lang.invoke APIs. SeeJEP 416: Reimplement Core Reflection with Method Handles.

Preview Features and Incubator Modules

SeeJEP 12: Preview Features for more information about preview features andJEP 11: Incubator Modules for more information about incubator modules.

Removed APIs, Tools, and Components

For more details on removals and deprecations, see:

• Finalization Deprecated for Removal
• APIs Removed in Java SE 18

In addition, there are security related updates that you need to be aware of. SeeSecurity Updates in JDK 18.

SeeJDK 17 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 17.

The following are some of the updates in Java SE 17 and JDK 17:

New Language Feature

• Sealed Classes, first previewed in Java SE 15, is a permanent feature in this release. Sealed classes and interfaces restrict which other classes or interfaces may extend or implement them. SeeJEP 409: Sealed Classes andSealed Classes inJava Platform, Standard Edition Java Language Updates guide.

Library Changes

• Applications can now configure context-specific and dynamically selected deserialization filters using a JVM-wide filter factory, which is invoked to select a filter for each individual deserialization operation. SeeJEP 415: Context-Specific Deserialization Filters andSerialization Filtering inJava Platform, Standard Edition Core Libraries guide.
• New interface types and implementations for pseudo-random number generators (PRNGs) are now available, including jumpable PRNGs and an additional class of splittable PRNG algorithms (LXM). SeeJEP 356: Enhanced Pseudo-Random Number Generators andPseudorandom Number Generators inJava Platform, Standard Edition Core Libraries guide.
• New Java 2D internal rendering pipeline for macOS is implemented using the Apple Metal API. This is an alternative to the existing pipeline, which uses the deprecated Apple OpenGL API. SeeJEP 382: New macOS Rendering Pipeline.

Other Changes

• By default, all internal elements of the JDK are strongly encapsulated, except for critical internal APIs such assun.misc.Unsafe. However, it will no longer be possible to relax the strong encapsulation of internal elements using a single command-line option, as it was possible in JDK 9 through JDK 16. SeeJEP 403: Strongly Encapsulate JDK Internals by Default.
• The floating-point operations are now consistently strict, rather than having both strict floating-point semantics (strictfp) and subtly different default floating-point semantics. SeeJEP 306: Restore Always-Strict Floating-Point Semantics.

Deprecations

• The Security Manager and APIs related to it have been deprecated for removal in a future release. SeeJEP 411: Deprecate the Security Manager for Removal.

Preview Features and Incubator Modules

SeeJEP 12: Preview Features for more information about preview features andJEP 11: Incubator Modules for more information about incubator modules.

Removed APIs, Tools, and Components

See:

• APIs Removed in Java SE 17
• Tools and Components Removed and Deprecated in JDK 17

In addition, there are security related updates that you need to be aware of. See:Security Updates in JDK 17.

SeeJDK 16 Release Notes for additional descriptions of the new features and enhancements, and API specification in JDK 16.

The following are some of the updates in Java SE 16 and JDK 16:

• The Java programming language is enhanced with pattern matching for theinstanceof operator. This feature allows common logic in a program, namely the conditional extraction of components from objects, to be expressed more concisely and safely. SeeJEP 394: Pattern Matching for instanceof andPattern Matching for instanceof inJava Platform, Standard Edition Java Language Updates guide.
• Records, first previewed in Java SE 14, is a permanent feature in this release. The earlier restrictions have been relaxed whereby the inner classes can declare members that are either explicitly or implicitly static. This includes record class members, which are implicitly static. SeeJEP 395: Records andRecord Classes inJava Platform, Standard Edition Java Language Updates guide.
• By default, all internal elements of the JDK are strongly encapsulated, except for critical internal APIs such assun.misc.Unsafe. You can choose the relaxed strong encapsulation that has been the default since JDK 9. SeeJEP 396: Strongly Encapsulate JDK Internals by Default andStrong Encapsulation in the JDK.
• UNIX domain socket channels have been integrated into JDK 16. SeeJEP 380: Unix-Domain Socket Channels andInternet Protocol and UNIX Domain Sockets NIO Example inJava Platform, Standard Edition Core Libraries.
• The Z Garbage Collector processes the thread stacks concurrently. This allows all roots in the JVM to be processed by ZGC in a concurrent phase. SeeJEP 376: ZGC: Concurrent Thread-Stack Processing andThe Z Garbage Collector inJava Platform, Standard Edition HotSpot Virtual Machine Garbage Collection Tuning Guide.
• Thejpackage tool, which was incubated in JDK 14, is now a permanent feature. The tool packages a Java application into a platform-specific package that includes the necessary dependencies. SeeJEP 392: Packaging Tool andJava Platform, Standard Edition Packaging Tool User's Guide.
• Elastic metaspace overhauls the VM-internal metaspace- and class-space-implementation. The unused HotSpot class-metadata (that ismetaspace) memory is returned to the operating system. It reduces the metaspace footprint and simplify the metaspace code in order to reduce maintenance costs. SeeJEP 387: Elastic Metaspace.

Preview Features and Incubator Modules

SeeJava Language Preview Feature for more information about preview features.

Removed APIs, Tools, and Components

See:

• API Removed in Java SE 16
• Tools and Components Removed and Deprecated in JDK 16

In addition, there are security related updates that you need to be aware of. See:Security Updates in JDK 16.

SeeJDK 15 Release Notes for the complete list of new features and enhancements in JDK 15.

The following are some of the updates in Java SE 15 and JDK 15:

• Text Blocks, first previewed in Java SE 13, is a permanent feature in this release and can be used without enabling preview features.

  Text blocks are multiline string literals that avoid the need for most escape sequences, automatically format the string in a predictable way, and give the developer control over the format when desired. SeeJEP 378: Text Blocks andProgrammer's Guide to Text Blocks.

• The Z Garbage Collector (ZGC) is ready to use in production and no longer an experimental feature. Enable ZGC by using the command-line option-XX:+UseZGC. SeeJEP 377: ZGC: A Scalable Low-Latency Garbage Collector (Production).
• Hidden classes are classes that cannot be used directly by the bytecode of other classes. Hidden classes are intended for use by frameworks that generate classes at run time and use them indirectly through reflection. SeeJEP 371: Hidden Classes.

Preview and Incubator Features

SeeJava Language Preview Feature for more information about preview features.

Removed APIs, Tools, and Components

See:

• APIs Removed in Java SE 15
• Tools and Components Removed and Deprecated in JDK 15

In addition, there are security related updates that you need to be aware of. See:Security Updates in JDK 15.

The following are some of the changes in Java SE 14 and JDK 14:

• Switch is extended so it can be used as either a statement or an expression, so that both forms can use either traditionalcase ... : labels (with fall through) or newcase ... -> labels (with no fall through), with a further new statement for yielding a value from a switch expression. SeeJEP 361: Switch Expressions (Standard) andJava Language Changes.
• G1 is enhanced to improve allocation performance on non-uniform memory access (NUMA) memory systems. SeeJEP 345: NUMA-Aware Memory Allocation for G1.
• JDK Flight Recorder data is now available as a data stream allowing for continuous monitoring. SeeJEP 349: JFR Event Streaming.
• New JDK-specific file mapping modes have been added so that theFileChannel API can be used to createMappedByteBuffer instances that refer to non-volatile (NVM) memory. SeeJEP 352: Non-Volatile Mapped Byte Buffers.
• Allows currencies to be formatted with locale-specific accounting formats, for example, ($3.27) instead of -$3.27. SeeAccounting Currency Format Support.
• Enhancedcom.sun.management.OperatingSystemMXBean to ensure that it reports values based on the current operating environment, such as a container environment. The MXBean for tools to get information on the operating system has been improved for container environments. SeeOperatingSystemMXBean made container aware.

Experimental, Preview, and Incubator Features

Removed APIs, Tools, and Components

See:

• APIs Removed in Java SE 14
• Features and Components Removed in JDK 14

In addition, there are security related updates that you need to be aware of. See:Security Updates in JDK 14.

The following were some of the important enhancements in Java SE 13 and JDK 13:

• Dynamic CDS Archiving extends application class-data sharing (ApsCDS), which allows dynamic archiving of classes when the Java application exits. SeeJEP 350: Dynamic CDS Archives.
• Text blocks were added to Java language, which provide developers with control over the format when desired. This is a preview language feature. SeeJEP 355 Text Blocks (Preview) andJEP 12: Preview Language and VM Features.
• Theswitch expression, a preview language feature, was extended to be used as either a statement or an expression, so that both forms can use either traditional labels (with fall through) or new labels (with no fall through). It is used with a further new statement for yielding a value from aswitch expression. SeeJEP 354: Switch Expressions (Preview) andJEP 12: Preview Language and VM Features.
• The implementation used byjava.net.Socket andjava.net.ServerSocket APIs was replaced with a simpler and more modern implementation that is easy to maintain and debug. SeeJEP 353: Reimplement the Legacy Socket API.
• Support for Unicode 12.1. SeeUnicode 12.1.
• ZGC was enhanced to return unused heap memory to the operating system, which enhances the memory footprint of the applications. SeeJEP 351 ZGC Uncommit Unused Memory.

The following were some of the important additions and updates in Java SE 12 and JDK 12:

• JVM Constants API was introduced to model nominal descriptions of key class-file and run-time artifacts, in particular constants that were loadable from the constant pool. SeeJVM Constant API.
• Theswitch statement was extended so that it can be used either as a statement or an expression. This is a preview language feature. SeeJEP 325: Switch Expressions (Preview) andJEP 12: Preview Language and VM Features.
• Support for Unicode 11.0. SeeUnicode 11.0.
• Square character support was provided for the Japanese Reiwa Era, which began on May, 2019. SeeSquare character support.
• TheNumberFormat added support for formatting a number in its compact form. SeeCompact Number Formatting Support.

JDK 11 had some significant changes too. As JDK 11 is a long term support (LTS) release, you should be familiar with the following important changes in JDK 11 release:

• Oracle no longer offers JRE and Server JRE downloads; consequently, Auto-Update is not available anymore.

• Java Web Start, Java Plugin, and Java Control Panel are not available in JDK. SeeRemoval of the Deployment Stack.

• JavaFX is no longer included in the JDK. It is now available as a separate download fromhttps://openjfx.io/.

• JAXB and JAX-WS are no longer bundled with JDK. SeeRemoval of Java EE and CORBA Modules.