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
If you're using log4j
Exception e = new Exception();
log.error("error here", e);
will print the stacktrace to your log.
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2 Comments
Paul Tomblin
The 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().
Chris Nava
Use logging. Printing to stdout/stderr should only be done by OS utilities and "Hello World" apps.
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.
Just creating an arbitrary exception does the trick for me:
System.out.println("Oops, the bad thing happened");
new IllegalStateException().printStackTrace();
3 Comments
Tim Frey
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.
Dan Dyer
Thread.dumpStack() is easier if you just want to send it to stderr (saves having to loop over the stack trace elements yourself).
izb
This method is useful in JavaME which doesn't have getStackTrace or dumpStack methods on Thread.
As well as what @jjnguy said, if you don't have an exception, you can also call Thread.getStackTrace().
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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.
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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);
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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.
