Java Class Question

I've been trying to access a java class as a function.

My code is:
---------------------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
   xmlns:Date="java:java.util.Date" >
   <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>

<xsl:variable name="myDate" select="Date:new()"/>   
<xsl:variable  name="today" select="Date:toString($myDate )" /> 

------------------------------------------------------------

When I run this I get

Warning: popContextNodeList when stack is empty!
(Location of error unknown)XSLT Error 
(javax.xml.transform.TransformerException)
: java.lang.ArrayIndexOutOfBoundsException: -1

Does anyone have a suggestion on how to fix this?
Does anyone have a good working example?