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24  */
25 
26 package java.util;
27 
28 /**
29  * <p>
30  * The root class from which all event state objects shall be derived.
31  * <p>
32  * All Events are constructed with a reference to the object, the "source",
33  * that is logically deemed to be the object upon which the Event in question
34  * initially occurred upon.
35  *
36  * @since JDK1.1
37  */
38 
39 public class EventObject implements java.io.Serializable {
40 
41     private static final long serialVersionUID = 5516075349620653480L;
42 
43     /**
44      * The object on which the Event initially occurred.
45      */
46     protected transient Object  source;
47 
48     /**
49      * Constructs a prototypical Event.
50      *
51      * @param    source    The object on which the Event initially occurred.
52      * @exception  IllegalArgumentException  if source is null.
53      */
EventObject(Object source)54     public EventObject(Object source) {
55         if (source == null)
56             throw new IllegalArgumentException("null source");
57 
58         this.source = source;
59     }
60 
61     /**
62      * The object on which the Event initially occurred.
63      *
64      * @return   The object on which the Event initially occurred.
65      */
getSource()66     public Object getSource() {
67         return source;
68     }
69 
70     /**
71      * Returns a String representation of this EventObject.
72      *
73      * @return  A a String representation of this EventObject.
74      */
toString()75     public String toString() {
76         return getClass().getName() + "[source=" + source + "]";
77     }
78 }
79