Native Java agents are usually used to observe the JVM. With a little HotSpot knowledge, they can also help you solve problems that are difficult or impossible to tackle with the standard Java APIs.

In this talk, we’ll look at six practical and surprising use cases. We’ll show how to sanitize heap dumps before they are written to disk for GDPR compliance, turn JDK log events into JFR events, react to heap watermarks without polling, and disable garbage collection at runtime for controlled benchmarking.

We’ll also explore more unusual applications: hiding Java threads from thread dumps and suppressing asynchronous interruptions such as Thread.interrupt().

Along the way, we’ll look at HotSpot’s internal data structures and classes, and see how we use native hot patching to modify a running JVM. While these techniques are low-level and often version-specific, they can give you powerful new tools for solving JVM problems.