active when the method is
called).</p>

<p>If the implementation of <code>Birthday</code> ensures, that none of its fields
could hold a <code>null</code> value and gender contains a valid value, then we could drop the 
<code>null</code> condition in the <code>marshal</code> method and in <code>unmarshal</code>
we could omit the loop as well as the comparison of the tag names:</p><div class="Source Java"><pre>package com.thoughtworks.xstream.examples;

import java.util.Calendar;

import com.thoughtworks.xstr