Core Java

Oracle JDK 9 Early Access Documentation Updated

Raymond Gallardo‘s 4 April 2017 post Early Access documentation for Oracle JDK 9 has been updated today announces updates to the Oracle JDK9 Documentation Early Access page. Gallardo highlights a few of the updated sections including What’s New in Oracle JDK 9, Oracle JDK 9 Migration Guide, HotSpot Virtual Machine Garbage Collection Tuning Guide (including Garbage-First Garbage Collector Tuning), javapackager tool for “packaging Java and JavaFX applications,” and XML Catalog API.

The Main Tools to Create and Build Applications section features information on jlink (JEP 282), jmod (create and show contents of Project Jigsaw JMOD files), and jdeprscan (static analysis tool that scans … for uses of deprecated API elements). There is also information on jhsdb for obtaining “specific information from a hanging or crashed JVM.”

I summarized some of the tools and features being removed from the JDK with Java 9 in the post JDK 9 is the End of the Road for Some Features. Some of these are spelled out with additional details in the section Removed Tools. The Changes to Garbage Collection section similarly shows changes and removals in Java 9 of options and commands related to garbage collection. The section Changes to the Installed JDK/JRE Image outlines removal of things such as rt.jar and tools.jar, the extension mechanism, and the endorsed standards override mechanism.

The section Enable Logging with the JVM Unified Logging Framework demonstrates how to “use -Xlog option to configure or enable logging with the Java Virtual Machine (JVM) unified logging framework.” The Changes to GC Log Output section explains how to use this -Xlog with gc (-Xlog:gc) for logging related to garbage collection and points out that “the -XX:+PrintGCDetails and -XX:+PrintGC options have been deprecated.”

I previously blogged on the future of the Concurrent-Mark-Sweep garbage collector. The Java SE 9 HotSpot Virtual Machine Garbage Collection Tuning Guide states, “The CMS collector is deprecated. Strongly consider using the Garbage-First collector instead.”

The main Oracle JDK 9 Documentation Early Access page is at and its Developer Guides link provides direct references to guides such as Troubleshooting Guide, HotSpot Virtual Machine Garbage Collection Tuning Guide, Java Scripting Programming Guide, Java Language Updates, and Migration Guide.

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