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Java / Java 17 Garbage Collection Interview Questions

How do you enable GC logging in Java 17?

Java 17 uses the unified JVM logging framework (introduced in JDK 9) via the -Xlog flag, which replaced the older per-collector flags like -XX:+PrintGCDetails.

A typical production-ready configuration looks like:

-Xlog:gc*:file=gc.log:time,uptime,level,tags:filecount=5,filesize=20M

Here, gc* selects all GC-related log tags, the file= section directs output to a rotating log file, the decorators (time,uptime,level,tags) control what metadata prefixes each line, and filecount/filesize enable log rotation so files don't grow unbounded.

You can also narrow the scope, for example -Xlog:gc+heap=debug to focus on heap-region-level detail when diagnosing a specific issue.

GC logging in Java 17 is configured primarily through:
Specifying filecount and filesize with -Xlog is useful because it:

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