How to fill what printStackTrace() output into a String?

[Chris Wahl]

Hi, all 

I want to get the exception stack trace and I 'd like to use a 
String to contain the info, How can I do?

I am thinking about this: (ex is an instance of Exception )

          PrintStream trace = new PrintStream();
          ex.printStackTrace(trace);
          String str = doSomeThing (trace); 

Then how to write the function doSomeThing() ?

Is there any elegance solution?

TIA
Chris