The Java tool jcmd ("j command") sends diagnostic commands to the JVM, which will react by supplying the desired information: from finalizer queues to heap and thread dumps, from GC insights to virtual thread scheduler statistics. At the moment, this requires a running JVM, but once candidate JEP 528 is adopted, a lot of that information can be seamlessly extracted from a crashed JVM's core dump, allowing easy post-mortem analysis.