Let's first verify that the agent is aware that sensor needs to be active.
Go to Agents Overview, select the agent that should have that rule on, and on the bottom side, swtich to the tab "Deployed Sensors" - can you find the method there?
Then this explains why you're not seeing any results. This might mean that there is an issue with the hot sensor placement and you might have to manually restart the processes for the rule to be applied successfully.
Unfortunately I do not believe Dynatrace AppMon is able to instrument Java Native methods because they are not really "Java" code. Their implementations are actually written in a non-Java language like C, C++ or Assembly. Because of this, there isn't really "Java" code to instrument.
I hope this helps!
- Kasey C.