And call that method from within the method that needs to know who its caller is. However, a word of warning: the index of the calling frame within the list could vary according to the JVM! It all depends on how many layers of calls there are within getStackTrace before you hit the point where the trace is generated. A more robust solution would be to get the trace, and iterate over it looking for the frame for getCallingMethodName, then take two steps further up to find the true caller.
You don't even have to do this in the code. You can attach the Java HPROF to your process and at any point hit Control-\ to output heap dump, running threads, etc . . . without mucking up your application code. This is a bit outdated, Java 6 comes with the GUI jconsole, but I still find HPROF to be very useful.
You can also send a signal to the JVM to execute Thread.getAllStackTraces() on a running Java process by sending a QUIT signal to the process.
On Unix/Linux use:
kill -QUIT process_id, where process_id is the process number of your Java program.
On Windows, you can press Ctrl-Break in the application, although you usually won't see this unless you're running a console process.
JDK6 introduced another option, the jstack command, which will display the stack from any running JDK6 process on your computer:
jstack [-l] <pid>
These options are very useful for applications which are running in a production environment and cannot be modified easily. They're especially useful for diagnosing runtime deadlocks or performance problems.
Java 9 introduced the StackWalker and supporting classes for walking the stack.
Here are a few snippets from the Javadoc:
The walk method opens a sequential stream of StackFrames for the current thread and then applies the given function to walk the StackFrame stream. The stream reports stack frame elements in order, from the top most frame that represents the execution point at which the stack was generated to the bottom most frame. The StackFrame stream is closed when the walk method returns. If an attempt is made to reuse the closed stream, IllegalStateException will be thrown.
...
To snapshot the top 10 stack frames of the current thread,