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Johan Lübcke
Johan Lübcke

Reputation: 20224

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

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.

Upvotes: 12

Views: 17171

Answers (8)

minipif
minipif

Reputation: 4866

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);

Upvotes: 2

shsteimer
shsteimer

Reputation: 28810

If you're using log4j

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

will print the stacktrace to your log.

Upvotes: 20

sleske
sleske

Reputation: 83597

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.

Upvotes: 1

Christoffer
Christoffer

Reputation:

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.

Upvotes: 6

Dan Dyer
Dan Dyer

Reputation: 54475

Thread.dumpStack();

Upvotes: 12

Paul Tomblin
Paul Tomblin

Reputation: 182782

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

Upvotes: 3

Johan Lübcke
Johan Lübcke

Reputation: 20224

Just creating an arbitrary exception does the trick for me:

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

Upvotes: 4

jjnguy
jjnguy

Reputation: 138874

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.

Upvotes: 2

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