I want to do some scripting in xsl using Java. (and this is my first time!!!)

I don't think you actually "do scripting" using Java in Xalan.
Xalan allows calls to static Java methods as extension functions
in XPath expressions. See
 http://xml.apache.org/xalan-j/extensions.html#java-namespace
and the following example.

<xalan:script language="javaclass" src="xalan:java.util.Date" />

<xsl:variable name="date" select="Date:toString(Date:new())" xmlns:Date="xalan:java.util.Date" />
<DOB>$date</DOB>

            ^^^^^
Likely another mistake, you probably want
 <DOB><xsl:value-of select="$date"/></DOB>