Function
The thread snapshot used to generate the current moment of the virtual machine (commonly referred to as a threaddump or Javacore file). A thread snapshot is a collection of method stacks that each thread in the current virtual machine is executing, and the primary purpose of generating the thread snapshot is to locate the cause of a long pause on threads, such as inter-thread deadlocks, dead loops, long waits that are caused by requests for external resources, and so on, which are common causes of long-running threads. When a thread pauses, you can see the call stack of each thread by Jstack, and you know what the unresponsive thread is doing in the background, or what resources are waiting for it.
Example
Description -F: Force output thread Stack-L: Displays additional information about the lock in addition to the stack-m: If you call to a local method, you can display the C + + stack
Jstack (Stack Trace for Java)