Java 21 Now Feature Complete
Written by Kay Ewbank   
Thursday, 17 August 2023

Java and JDK 21 are now feature complete, and are in Rampdown Phase Two. Java 21 is the new Long Term Support (LTS) version, meaning it will be supported for at 5 years by Oracle, and both Java 21 and JDK 21 come with 15 JEPs (Java Enhancement Proposals).

The arrival of this stage for standard Java JDK 21 was announced by the Open JDK group. Oracle will release the new version under a commercial license for those using the Oracle JDK release as part of an Oracle product or service, or for those who want to be able to get commercial support.


One hightlight of the new version is full support for virtual threads. Virtual threads are lightweight threads that significantly reduce the effort of writing, maintaining, and observing high-throughput concurrent applications.

The aim of the developers in adding virtual thread support was to enable server applications written in the simple thread-per-request style to scale with near-optimal hardware utilization. Since they were introduced in JDK 19, virtual threads have been changed so they always support thread-local variables.

A preview has also been included of string templates. These complement Java's existing string literals and text blocks by coupling literal text with embedded expressions and template processors to produce specialized results.

Other improvements include support for sequenced collections with a defined encounter order;and a preview of support for unnamed patterns, which match a record component without stating the component's name or type, and unnamed variables, which can be initialized but not used.

The Z garbage collector has also been improved so that it can maintain separate generations for young and old objects. The developers say this will allow ZGC to collect young objects — which tend to die young — more frequently, and will thus improve application performance. 

Oracle plans to release Java 21 at Oracle CloudWorld on September 19th.


More Information

JDK 21 Announcement

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