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.
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8 Answers
20
If you're using log4j
Exception e = new Exception();
log.error("error here", e);
will print the stacktrace to your log.
Samuel Edwin Ward
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shsteimer
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Dan Dyer
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1The downside is that dumpStack() only goes to stderr, and you can't send it somewhere else like you can with an exception or Thread.getStackTrace(). – Paul Tomblin Sep 10 '08 at 18:58
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4Use logging. Printing to stdout/stderr should only be done by OS utilities and "Hello World" apps. – Chris Nava Nov 16 '09 at 17:23
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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.
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Shouldn't one also step or recurse through e.getCause(), and get stack traces for all of those too? – slim Sep 23 '08 at 18:52
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4
Just creating an arbitrary exception does the trick for me:
System.out.println("Oops, the bad thing happened");
new IllegalStateException().printStackTrace();
Johan Lübcke
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I believe that this method will cause a warning in some IDEs, such as IntelliJ, because you're creating an exception but not throwing it. I recommend the Thread.getStackTrace() method which has the same logic but it's hidden from the developer. – Tim Frey Sep 10 '08 at 18:15
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Thread.dumpStack() is easier if you just want to send it to stderr (saves having to loop over the stack trace elements yourself). – Dan Dyer Sep 10 '08 at 18:29
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2This method is useful in JavaME which doesn't have getStackTrace or dumpStack methods on Thread. – izb Sep 10 '08 at 19:52
3
As well as what @jjnguy said, if you don't have an exception, you can also call Thread.getStackTrace().
Paul Tomblin
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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);
minipif
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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.
jjnguy
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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.
