The JDK 8 API docs do not show serialized forms for Swing classes.
See, for example, JScrollBar here:
https://docs.oracle.com/javase/8/docs/api/javax/swing/JScrollBar.html

Note:
<dl>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="../../javax/swing/JScrollPane.html" title="class in javax.swing"><code>JScrollPane</code></a></dd>
</dl>

The corresponding page for JDK 9 onwards, has a "See Also" link to the serialized form, but the link is a broken link. In both 8 and 9, there is no entry for Swing classes on the serialized-form page.
https://docs.oracle.com/javase/9/docs/api/javax/swing/JScrollBar.html

Note:
<dl>
<dt><span class="simpleTagLabel">Since:</span></dt>
<dd>1.2</dd>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="../../javax/swing/JScrollPane.html" title="class in javax.swing"><code>JScrollPane</code></a>,
<a href="../../serialized-form.html#javax.swing.JScrollBar">Serialized Form</a></dd>
</dl>