Java 27 (JDK 27) became generally available on September 15, 2026. It adds nine JEPs spanning language features, concurrency, cryptography, garbage collection, object layout and diagnostics, alongside smaller release-note changes. The practical highlights are post-quantum hybrid key exchange for applicable TLS use, G1 as the default garbage collector in all environments, compact object headers by default, and in-process redaction in Java Flight Recorder. Several APIs remain previews or incubating, so they are not yet permanent Java SE features.
What’s new in Java 27?
Oracle’s JDK 27 release announcement identifies nine JEP enhancements. Four are preview features and one is incubating; the rest are permanent features or runtime changes. The release notes also list changes beyond those nine JEPs, so the JEP list is not a complete inventory.
| Feature | What it does | Status in JDK 27 |
|---|---|---|
JEP 532: Primitive Types in Patterns, instanceof, and switch |
Extends pattern matching and instanceof/switch to primitive types. |
Fifth preview |
| JEP 531: Lazy Constants | Provides an API for unmodifiable data that can initialize later while still allowing the JVM to treat values as constants for optimization. | Third preview |
| JEP 533: Structured Concurrency | Groups related tasks running in different threads so they can be managed as a unit, with the aim of simplifying error handling, cancellation, reliability and observability. | Seventh preview |
| JEP 537: Vector API | Expresses vector computations that can compile at runtime to CPU vector instructions on supported systems. | Twelfth incubator |
| JEP 527: Post-Quantum Hybrid Key Exchange for TLS 1.3 | Combines quantum-resistant and traditional key exchange algorithms. Oracle says applications using javax.net.ssl benefit by default without code changes. |
Included in the release |
| JEP 538: PEM Encodings of Cryptographic Objects | Adds an API for encoding and decoding cryptographic keys, certificates and certificate revocation lists in PEM format. | Third preview |
| JEP 523: Make G1 the Default Garbage Collector in All Environments | Makes G1 the default collector across environments, rather than only in server environments. | Default change |
| JEP 534: Compact Object Headers by Default | Changes HotSpot’s default object-header layout. Oracle reports a reduction from 96 bits to 64 bits on 64-bit architectures. | Default change |
| JEP 536: JFR In-Process Data Redaction | Redacts command-line arguments and initial values of environment variables and system properties in Java Flight Recorder recordings before data leaves the process. | Included in the release |
Oracle describes broader improvements to cryptography, performance, I/O, diagnostics and documentation in its JDK 27 announcement. Those are vendor characterizations, not guarantees that every application will see a performance gain.
Which Java 27 features are still in preview or incubation?
Preview and incubating features are provisional, unlike permanent Java SE features. In JDK 27, primitive patterns, lazy constants, structured concurrency and PEM encoding are previews; the Vector API is incubating. Their presence does not mean their APIs are final or that code using them will work unchanged in a later release.
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Before adopting one, consult the Java 27 language documentation and JDK release documentation for the exact compiler and runtime flags. Check that your build, deployment environment and organization’s policy permit preview or incubator features. Treat them as a deliberate compatibility choice rather than a routine dependency.
What changes matter most when upgrading?
Runtime defaults: G1 and compact object headers
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Security: TLS and key encodings
JEP 527 adds post-quantum hybrid key exchange for TLS 1.3. Oracle says applications using javax.net.ssl benefit by default without code changes. Teams should review their TLS configuration and compatibility requirements rather than assuming every TLS stack or external endpoint behaves identically.
JDK 27 also changes the default private-key encoding for ML-KEM and ML-DSA to seed. Oracle’s consolidated release notes warn that older JDKs do not accept keys generated in this default format by default. Where older-runtime compatibility is required, the notes describe selecting expandedKey and translating keys.
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Operations: Java Flight Recorder and diagnostics
JFR’s in-process redaction covers command-line arguments and the initial values of environment variables and system properties in recordings before that data leaves the process. Review recording and observability settings to understand what information your organization still collects and how it handles it.
Other release-note additions include a jcmd VM.security_properties diagnostic, Bash completion for jcmd, current open-file-descriptor counts in diagnostics, TLS 1.3 certificate compression using zlib, and Foreign Function and Memory API support for initializing thread-local execution state before downcalls. See Oracle’s JDK 27 release notes for the full list.
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Is Java 27 released, and how long is it supported?
Yes. Oracle announced JDK 27 general availability on September 15, 2026. The Java SE specifications index records Java SE 27 as released in September 2026 as JSR 402, distinguishing the platform specification from the JDK implementation. See Oracle’s Java SE Specifications index.
Support dates depend on the JDK vendor. Oracle says it will provide JDK 27 updates until March 2027, when Oracle JDK 28 supersedes it. AWS says Amazon Corretto 27 is available for Linux, Windows and macOS and will be supported through April 2027. These are separate vendor commitments, not a universal Java 27 end-of-support date. Details are in Oracle’s announcement and AWS’s Corretto 27 availability notice.
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Should you upgrade to Java 27?
Evaluate the upgrade against your application’s compatibility needs and the features you intend to use. The runtime default changes and security additions may make it relevant even if you do not adopt preview APIs; teams considering previews or the Vector API should account for their provisional status.
Quick Recap
- Read Oracle’s release notes and significant changes guide, checking source, binary and behavioral compatibility separately.
- Test the G1 and object-header defaults on a representative workload, measuring the outcomes that matter to your service rather than assuming a universal gain.
- Check TLS integrations, cryptographic key exchange and any ML-KEM or ML-DSA keys that must interoperate with older runtimes.
- Confirm whether preview or incubator features are permitted in your build and deployment environments, and record the flags and version assumptions they require.
- Choose a JDK distribution based on its own support policy and platform coverage; do not infer one vendor’s update window from another’s.
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