Why am I getting an empty stacktrace while creating my own exception?

Question

I am inheriting Exception class for creating my own exception. Something like the code below

public class ApplicationException extends Exception {
  ApplicationException(String errorMessage) {
    super(errorMessage); 
  }
}

The problem is that the stacktrace is always empty. The below code will write nothing to the console.

ApplicationException(String errorMessage) {
  super(errorMessage); 
  System.out.println(this.getStackTrace());
}

I don't understand why it is empty because the Throwable(String) is calling fillInStackTrace method. Is there a way to fill in Stack or is it something else that I should do?

why don't you use printStackTrace() instead of the SOP call? — Stultuske
– Stultuske, Commented May 23, 2014 at 15:46
When I new up your exception in main, this.getStackTrace() gives me an object, and this.printStackTrace() prints the stack just fine. How are you using your exception in code? — azurefrog
– azurefrog, Commented May 23, 2014 at 15:47
I use the below code to report my exception t to eclipse errorlog. But it shows that I don't have stacktrace. final Status status = new Status(severity, Activator.PLUGIN_ID, msg + className, t); logger.log(status); — Govan
– Govan, Commented May 23, 2014 at 15:53

Boann · Accepted Answer · 2014-05-23 15:47:00Z

6

The stack trace is not empty. It's just that it's an array, and the default toString() of an array doesn't show its elements, only its class name and hashCode (e.g., [Ljava.lang.StackTraceElement;@b0cf5f). Call:

this.printStackTrace();

or loop through the array and display its contents manually, and you will see the stack trace.

answered May 23, 2014 at 15:47

Boann

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6 Comments

Govan Over a year ago

yes you are write. But then it is strange. I am using eclipse and I am reporting my errors to Eclipse ErrorLog. It showing that my exceptions don't have stack trace.

Boann Over a year ago

@Govan Well... they do.

mikea Over a year ago

This is only partly correct. The exception won't have a stacktrace until it has been thrown. Up until that time the printStackTrace will report the current stacktrace.

Boann Over a year ago

@mikea That's not true. Display the stack trace of an exception that was created and returned from (but not thrown by) a method call, and you will see the stack trace includes that method, showing that the stack trace is filled in at exception creation time, whether it has been thrown or not. Also see the documentation of Throwable, which says: "A throwable contains a snapshot of the execution stack of its thread at the time it was created."

Bombe Over a year ago

Also, a Throwable is free return an empty array of stack traces from the getStackTrace() method.

|

Community · Accepted Answer · 2017-05-23 12:16:49Z

4

this.getStackTrace() returns a StackTraceElement[]. Arrays never override toString, so printing it just yields something like:

[Ljava.lang.StackTraceElement;@1a23b006

You may want to invoke printStackTrace() instead. If you don't care about its causes (in your case, it won't have any), you can just iterate over the StackTraceElement objects in the array and print each one out.

In fact, if all you want is the stack trace, you can do without the exception altogether: Thread.currentThread().getStackTrace() gets you the same StackTraceElement[].

edited May 23, 2017 at 12:16

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answered May 23, 2014 at 15:47

yshavit

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Comments

mikea · Accepted Answer · 2014-05-23 15:53:38Z

0

At the point that you create a new exception you haven't thrown it so it won't have a stack trace.

EDIT:

Expanding on this. The fillInStackTrace in throwable sets the stacktrace of the expection to an empty array of stack trace elements. getStackTrace returns this stacktrace. It printStackTrace finds the stacktrace set to the default empty array it prints the current stack trace where it was called from, otherwise it prints the stacktrace contained in the exception.

edited May 23, 2014 at 15:53

answered May 23, 2014 at 15:43

mikea

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5 Comments

yshavit Over a year ago

Except that I do see a stack trace if I do new Exception().printStackTrace().

azurefrog Over a year ago

Not true. If you just new one up and put a this.printStackTrace() in the constructor, it prints the line that it was instantiated on.

Govan Over a year ago

i don't want to throw my exeptions. is it a way to fill in stacktrace?

mikea Over a year ago

So, you just want to print the stack trace in a point in your code?

Boann Over a year ago

"The fillInStackTrace in throwable sets the stacktrace of the exception to an empty array of stack trace elements." No it doesn't...?

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