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Design issue: Extensibility"></td></tr><tr><td bgcolor="ffffff" width="15"> </td><td bgcolor="ffffff" width="12"> </td><td valign="top" align="left" bgcolor="ffffff" width="*"><p><br x="7"><table cellspacing="0" cellpadding="0" border="0"><tr><td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>Plan for hooks</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr> page 3 of 3</nobr></font></td></tr></table><br x="7"><br x="7"></p><font size="2" face="Verdana, Arial, Helvetica"><p>
It's important to think ahead to the kinds of customizations a user of your library is going to want to make. The previous example was obvious -- you have to provide a way for the subclass to actually use the incoming connections or your program won't do anything useful.
</p><p>
But if you don't think ahead, some other customizations might not
occur to you. Instead, they'll occur to the user, who will wish that you
had thought of them in the first place.
</p><p>
In our sample library, there is a method in <code style="font-family: Courier New, Courier, monospace; font-size: 12">Server</code>
called <code style="font-family: Courier New, Courier, monospace; font-size: 12">cleanUp()</code>. This method is called by the server's
background thread just before it exits. The base server doesn't need
to do anything in this method, so it is empty:
</p><p>
<pre><code style="font-family: Courier New, Courier, monospace; font-size: 12">
// Put any last-minute clean-up stuff in here
protected void cleanUp() {
}
</code></pre>
</p><p>
<b>Note:</b> Do not declare this method <code style="font-family: Courier New, Courier, monospace; font-size: 12">abstract</code>, as it would require the user to implement this method, which, in some cases, isn't necessary.
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