This section demonstrates you to change the Preference values in a Preference node.

Listening for Changes to Preference Values in a Preference Node

     

This section demonstrates you to change the Preference values in a Preference node. You can see in the given example, we have used the class PreferenceChangeEvent which occurs when a preference is added, changed, or removed from a preference node if the application contains Listener and modifier. The method e.getNode() returns the preference node that changed. The method e.getKey() returns the key of the preference that was changed. The method getNewValue() returns the new value for the preference.

prefs.put("key", "Hello")- This method will add the preference to the specified node.

prefs.put("key", "Hello World")- This method will modify the preference.

prefs.exportSubtree(System.out)- This method emits an XML document representing all the preferences contained in the node.

prefs.remove("key")- This method will removes the value associated with the specified key in the preference node

Here is the code of ChangesToPreferenceValues.java

import java.io.*; import java.util.prefs.*; public class ChangesToPreferenceValues{ public static void main(String[]args) throws Exception{  Preferences prefs = Preferences.userRoot().node("Preference");  prefs.addPreferenceChangeListener(new PreferenceChangeListener() {  public void preferenceChange(PreferenceChangeEvent e) {  Preferences node = e.getNode();  String key = e.getKey();  String newValue = e.getNewValue();   }   });  prefs.put("key", "Hello");  prefs.put("key", "Hello World");  prefs.exportSubtree(System.out);  prefs.remove("key");  } }

When you run the above code, you will see that the value is added and then modified. After that, the key and its value will be removed.

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