1. Oracle JDK Migration Guide
  2. Significant Changes in the JDK

2 Significant Changes in the JDK

Before migrating your application to the latest JDK release, you must understand what the updates and changes are between it and the previous JDK release. If you are migrating from JDK 8, you should also be familiar with the differences between JDK 8 and later releases that are described in Migrating From JDK 8 to Later JDK Releases.

See the following sections to learn about some of the significant changes in latest JDK releases.

Significant Changes in JDK 17 Release

See JDK 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. See JEP 409: Sealed Classes and Sealed Classes in Java Platform, Standard Edition Java Language Updates guide.

Library Changes

Other Changes

  • By default, all internal elements of the JDK are strongly encapsulated, except for critical internal APIs such as sun.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. See JEP 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. See JEP 306: Restore Always-Strict Floating-Point Semantics.

Deprecations

Preview Features and Incubator Modules

See JEP 12: Preview Features for more information about preview features and JEP 11: Incubator Modules for more information about incubator modules.

Removed APIs, Tools, and Components

See:

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

Significant Changes in JDK 16 Release

See JDK 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:

Preview Features and Incubator Modules

See Java Language Preview Feature for more information about preview features.

  • Sealed classes, a preview feature from JDK 15, is re-previewed in this release. Sealed classes and interfaces restrict which other classes or interfaces may extend or implement them. There has been several refinements in this release, including the introduction of character sequences sealed, non-sealed, and permits as contextual keywords. See JEP 397: Sealed Classes (Second Preview) and Sealed Classes in Java Platform, Standard Edition Java Language Updates guide.
  • Initial iteration of an incubator module, jdk.incubator.vector, is provided to express vector computations. It reliably compiles at runtime to optimal vector hardware instructions on supported CPU architectures and thus achieve superior performance to equivalent scalar computations. See JEP 338: Vector API (Incubator).
  • Foreign Linker API is introduced that offers statically-typed, pure-Java access to native code. This API, along with the Foreign-Memory Access API (JEP 393), will simplify the otherwise error-prone process of binding to a native library. See JEP 389: Foreign Linker API (Incubator).
  • Foreign-Memory Access API allows Java programs to safely and efficiently access foreign memory outside of the Java heap. See JEP 393: Foreign-Memory Access API (Third Incubator).

Removed APIs, Tools, and Components

See:

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

Significant Changes in JDK 15 Release

See JDK 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. See JEP 378: Text Blocks and Programmer'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. See JEP 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. See JEP 371: Hidden Classes.

Preview and Incubator Features

See Java Language Preview Feature for more information about preview features.

Removed APIs, Tools, and Components

See:

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

Significant Changes in JDK 14 Release

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 traditional case ... : labels (with fall through) or new case ... -> labels (with no fall through), with a further new statement for yielding a value from a switch expression. See JEP 361: Switch Expressions (Standard) and Java Language Changes.
  • G1 is enhanced to improve allocation performance on non-uniform memory access (NUMA) memory systems. See JEP 345: NUMA-Aware Memory Allocation for G1.
  • JDK Flight Recorder data is now available as a data stream allowing for continuous monitoring. See JEP 349: JFR Event Streaming.
  • New JDK-specific file mapping modes have been added so that the FileChannel API can be used to create MappedByteBuffer instances that refer to non-volatile (NVM) memory. See JEP 352: Non-Volatile Mapped Byte Buffers.
  • Allows currencies to be formatted with locale-specific accounting formats, for example, ($3.27) instead of -$3.27. See Accounting Currency Format Support.
  • Enhanced com.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. See OperatingSystemMXBean made container aware.

Experimental, Preview, and Incubator Features

Removed APIs, Tools, and Components

See:

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

Significant Changes in JDK 13 Release

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

Significant Changes in JDK 12 Release

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

Significant Changes in JDK 11 Release

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: