ThreadInfo.getStackTrace() (JDK 1.5)

Question

The javadocs for ThreadInfo.getStackTrace() states the following:
If no stack trace was requested for this thread info, this method will return a zero-length array.
I'm using the ThreadMXBean to retrieve a list of all Thread ids, then the ThreadInfo by each Id. When I attempt to output the stack trace for each Thread, nothing is output. In short, my StackTraceElement array is zero length.
My current platform is Windows XP Pro SP2, and the JDK is 1.5.0_005. I'm guessing that my platform does support the stack trace frames. So the only other logical explanation I can imagine is that "no stack trace was requested," as stated in the above javadoc.
If I'm on the right trail, how does one request the most recent stack trace information to be populated on a ThreadInfo object? Does the default ThreadMXBean not do so?
Thanks for any insight.

Answer 1

If you already have a ThreadInfo, you can call getThreadInfo on its ID and specify a stack trace depth. For example:
ThreadMXBean tmbean; // initialized somewhere
ThreadInfo threadInfo; // initialized somewhere
// Update the thread info with the full stack trace
threadInfo = tmbean.getThreadInfo(threadInfo.getThreadId(), Integer.MAX_VALUE);
StackTraceElement[] stackTrace = threadInfo.getStackTrace();
By default, ThreadInfo has no stack trace elements.