How to Convert JDK8 GC Log Flags to JDK9 with Unified Logging: Introduction: JDK9 introduced unified logging for all JDK9 components. It provides a way for the users to configure the content of the logs. Since all the logs follow the unified format, it would make parsing easier. Users might have some difficulty finding the right tags and levels in JDK9, especially when migrating from JDK8. This post provides some basic back ground about unified logging in JDK9, and tags and levels in JDK9 corresponding to JDK8 flags for GC logging. JDK9 Unified Logging: With a JDK9 build, you can logging help by "java -Xlog:help". Here is the output from the command ./bin/java -Xlog:help -Xlog Usage: -Xlog[:[what][:[output][:[decorators][:output-options]]]] where 'what' is a combination of tags and levels on the form tag1[+tag2...][*][=level][,...] Unless wildcard (*) is specified, only log messages tagged with exactly the tags specified will be matc...