How do I in java add a stacktrace to my debugging printout

Question

What's the easiest way to print a stacktrace from a debugging printout? Often during testing you would like to know the callstack leading up to the situation provoking a debug message.

Answer 1

Thread.dumpStack();

Answer 2

If you're using log4j

Exception e = new Exception();
log.error("error here", e);

will print the stacktrace to your log.

Answer 3

If you want to save the stack trace into a String you can do this;

String exception = "";
for (StackTraceElement element : e.getStackTrace())
   exception += element.toString() + "\n";

Where e is, obviously, an exception.

Besides, it sounds very weird to autogenerate an own Exception just to find get a stack trace for a debug. Get Eclipse and use it's debug mode, it's really awesome.

Answer 4

Just creating an arbitrary exception does the trick for me:

System.out.println("Oops, the bad thing happened");
new IllegalStateException().printStackTrace();

Answer 5

As well as what @jjnguy said, if you don't have an exception, you can also call Thread.getStackTrace().

Answer 6

You should be catching the exception in a try-catch block.

e.getStackTrace();

That returns StackTraceElement[] that you can then interpret.

Also:

e.printStackTrace()

will...print the stacktrace.

Answer 7

To simply print the current stack trace to stderr, you can call:

Thread.dumpStack();

which itself just calls:

new Exception("Stack trace").printStackTrace();

To output to stdout rather than stderr, pass System.out to printStackTrace():

new Exception("Stack trace").printStackTrace(System.out);

Answer 8

Just because I needed it myself:

As inspired by answer How do I find the caller of a method using stacktrace or reflection? , you can retrieve the call stack using

StackTraceElement[] stackTraceElements = Thread.currentThread().getStackTrace()

Then you process and print/log whatever you are interested in. More work than using Thread.dumpStack(), but more flexible.