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25 
26 package java.util.prefs;
27 
28 import java.io.NotSerializableException;
29 
30 /**
31  * An event emitted by a <tt>Preferences</tt> node to indicate that
32  * a preference has been added, removed or has had its value changed.<p>
33  *
34  * Note, that although PreferenceChangeEvent inherits Serializable interface
35  * from EventObject, it is not intended to be Serializable. Appropriate
36  * serialization methods are implemented to throw NotSerializableException.
37  *
38  * @author  Josh Bloch
39  * @see Preferences
40  * @see PreferenceChangeListener
41  * @see NodeChangeEvent
42  * @since   1.4
43  * @serial exclude
44  */
45 public class PreferenceChangeEvent extends java.util.EventObject {
46 
47     /**
48      * Key of the preference that changed.
49      *
50      * @serial
51      */
52     private String key;
53 
54     /**
55      * New value for preference, or <tt>null</tt> if it was removed.
56      *
57      * @serial
58      */
59     private String newValue;
60 
61     /**
62      * Constructs a new <code>PreferenceChangeEvent</code> instance.
63      *
64      * @param node  The Preferences node that emitted the event.
65      * @param key  The key of the preference that was changed.
66      * @param newValue  The new value of the preference, or <tt>null</tt>
67      *                  if the preference is being removed.
68      */
PreferenceChangeEvent(Preferences node, String key, String newValue)69     public PreferenceChangeEvent(Preferences node, String key,
70                                  String newValue) {
71         super(node);
72         this.key = key;
73         this.newValue = newValue;
74     }
75 
76     /**
77      * Returns the preference node that emitted the event.
78      *
79      * @return  The preference node that emitted the event.
80      */
getNode()81     public Preferences getNode() {
82         return (Preferences) getSource();
83     }
84 
85     /**
86      * Returns the key of the preference that was changed.
87      *
88      * @return  The key of the preference that was changed.
89      */
getKey()90     public String getKey() {
91         return key;
92     }
93 
94     /**
95      * Returns the new value for the preference.
96      *
97      * @return  The new value for the preference, or <tt>null</tt> if the
98      *          preference was removed.
99      */
getNewValue()100     public String getNewValue() {
101         return newValue;
102     }
103 
104     /**
105      * Throws NotSerializableException, since NodeChangeEvent objects
106      * are not intended to be serializable.
107      */
writeObject(java.io.ObjectOutputStream out)108      private void writeObject(java.io.ObjectOutputStream out)
109                                                throws NotSerializableException {
110          throw new NotSerializableException("Not serializable.");
111      }
112 
113     /**
114      * Throws NotSerializableException, since PreferenceChangeEvent objects
115      * are not intended to be serializable.
116      */
readObject(java.io.ObjectInputStream in)117      private void readObject(java.io.ObjectInputStream in)
118                                                throws NotSerializableException {
119          throw new NotSerializableException("Not serializable.");
120      }
121 
122     // Defined so that this class isn't flagged as a potential problem when
123     // searches for missing serialVersionUID fields are done.
124     private static final long serialVersionUID = 793724513368024975L;
125 }
126