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<TITLE>Determining If a Preference Node Exists (Java Developers Almanac Example)
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    <A HREF="../java.util.prefs/pkg.html">java.util.prefs</A><font color="#666666" class="xsmall-font">
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  <h3>e415. Determining If a Preference Node Exists</h3>

A preference node is automatically created whenever
<code>Preferences.node()</code>, <code>Preferences.userNodeForPackage()</code>, or
<code>Preferences.systemNodeForPackage()</code> is called. To avoid creating a
node, you should first check to see if it exists.


<pre>    try {
        // Check if a node exists
        boolean exists = Preferences.userRoot().nodeExists("/foo"); // false
    
        // Get the node
        Preferences.userRoot().node(<font color="#0066ff"><i>"/foo"</i></font>);
    
        // Getting a non-existent node automatically creates it
        exists = Preferences.userRoot().nodeExists(<font color="#0066ff"><i>"/foo"</i></font>); // true
    
        // Remove the node
        Preferences prefs = Preferences.userRoot().node(<font color="#0066ff"><i>"/foo"</i></font>);
        prefs.removeNode();
    
        // The following would cause an IllegalStateException
        //exists = prefs.nodeExists(<font color="#0066ff"><i>"/foo"</i></font>);
    
        // Use the following to determine if the node has been removed
        exists = prefs.nodeExists(""); // false
    } catch (BackingStoreException e) {
    }
</pre>
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            &nbsp;<b>Related Examples</b></font></td>
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e411. <a class="eglink" href="GetRoot.html?l=rel">
    Getting the Roots of the Preference Trees
</a>
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e412. <a class="eglink" href="CreateNode.html?l=rel">
    Creating a Preference Node
</a>
<br>

e413. <a class="eglink" href="GetNode.html?l=rel">
    Retrieving a Preference Node
</a>
<br>

e414. <a class="eglink" href="RemNode.html?l=rel">
    Removing a Preference Node
</a>
<br>

e416. <a class="eglink" href="GetRelative.html?l=rel">
    Retrieving the Parent and Child Nodes of a Preference Node
</a>
<br>

e417. <a class="eglink" href="FindPref.html?l=rel">
    Finding a Preference in a Preference Tree
</a>
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        See also: 
<a class="eglink" href="/egs/java.util.prefs/pkg.html?l=rel#Events">
    Events
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<a class="eglink" href="/egs/java.util.prefs/pkg.html?l=rel#Importing%20and%20Exporting">
    Importing and Exporting
</a>&nbsp;&nbsp;

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