title: How to append an exception's StackTrace into a file in java?
body: <p>In java, when we catch a exception, we usually can use <code>printStackTrace()</code> method to print the error information, and we can also use <code>printStackTrace(PrintStream out)</code> to direct those information to a file. </p>
  
  <p>But how can I append those information into a existing file, just like using <code>out.append()</code>?</p>