OpenJDK 15 as the open-source implementation of the Java SE 15 Platform brings many improvements and new features. Among the OpenJDK 15 highlights are:
- The Z Garbage Collector (ZGC) was promoted from being experimental since JDK 11 to now being a product feature. G1 remains the default garbage collector while this low-latency, scalable GC is available for those wanting to make use of it. In now being official, the UnlockExperimentalVMOptions argument is no longer needed but just -XX:+UseZGC for enabling.
- The Shenandoah low-pause-time garbage collector was also promoted to being a production feature.
- Support for text blocks in the Java language as a multi-line string literal that avoids the need for most escape sequences.
- Removal of Solaris support for SPARC and x86_64. The Linux SPARC support has been removed too... For OpenJDK it's game over for Solaris and SPARC after it was deprecated in JDK 14.
- Sealed classes are in preview form This allows restricting what other classics or interfaces may extend/implement the "sealed" classes/interfaces.
- Support for hidden classes as classes that cannot be used directly by the bytecode of other classes.
- Removal of the Nashorn JavaScript Engine.
- Support for cryptographic signatures using EdDSA (Edwards-Curve Digital Signature Algorithm).
- Better out-of-the-box performance in select configurations.
There are also many other improvements with OpenJDK 15. More details and downloads via openjdk.java.net .