Oracle Announces Second Set of Java 9 Features Including Unified JVM Logging, Compiler Controls, and Module System Enhancements

Oracle has confirmed the last four Java 9 features, publishing a second set of JEPs after earlier announcing three new APIs and modular source code. This marks the first time Oracle has released a comprehensive Java 9 feature list.

Unified JVM Logging (JEP 158) : All JVM components will adopt a common logging format, changing how subsystems record events and adding unified command‑line options for logging.

More Compiler Control (JEP 165) : A suite of control options will give developers finer‑grained method‑level control over the HotSpot JIT compiler, allowing adjustments to compiler behavior and optimization settings.

Removal of Obsolete GC Combinations (JEP 214) : The outdated collector pairs DefNew + CMS, ParNew + SerialOld, and incremental CMS are eliminated, reducing maintenance cost and freeing resources to simplify HotSpot GC code, lower bugs, and improve remaining collectors.

Improving the Coin Project (JEP 213) : Originally created for small language tweaks in Java 7, the Coin project will now address legacy issues from those changes, without introducing a second version or soliciting new language proposals.

Java 9 will also support Datagram Transport Layer Security (DTLS) and introduce an HTML5‑formatted Javadoc tool.

Oracle announced a multi‑year warning‑removal project that improves import handling, suppresses warnings for deprecated classes, and reduces unnecessary alerts.

Java 9 Modularization Confirmed : Oracle reaffirmed its commitment to modularizing the JDK source, building on the Jigsaw effort (JEP 152 and JEP 201) that began earlier this year.

Reference: Will the Panama project be included in Java 9?

Java platform chief architect Mark Reinhold explained that replacing JARs with modules in the JRE and JDK will affect IDEs and tools that enumerate classes in runtime images, impacting a small class of applications.

According to Reinhold, a new detection mechanism (JEP 220) will make classes more resilient to future format changes, and he noted that “the JAR format has reached its end; it’s time to move forward,” causing some anxiety among developers, though existing applications will continue to run.

The first set of Java 9 features announced in August, which included three new APIs and three minor enhancements, received a lukewarm response from the Java community.

(Original source: Jaxenter translation; source: ImportNew‑进林)