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Class com.sun.java.swing.event.EventListenerList 

java.lang.Object
   |
   +----com.sun.java.swing.event.EventListenerList
public class EventListenerList
extends Object
implements Serializable
A class which holds a list of EventListeners. A single instance can be used to hold all listeners (of all types) for the instance using the lsit. It is the responsiblity of the class using the EventListenerList to provide type-safe API (preferably conforming to the JavaBeans spec) and methods which dispatch event notification methods to appropriate Event Listeners on the list. The main benefits which this class provides are that it is relatively cheap in the case of no listeners, and provides serialization for eventlistener lists in a single place, as well as a degree of MT safety (when used correctly). Usage example: Say one is defining a class which sends out FooEvents, and wantds to allow users of the class to register FooListeners and receive notification when FooEvents occur. The following should be added to the class definition: 
EventListenerList listenrList = new EventListnerList();
FooEvent fooEvent = null;
public void addFooListener(FooListener l) {
listenerList.add(FooListener.class, l);
}
public void removeFooListener(FooListener l) {
listenerList.remove(FooListener.class, l);
}
// Notify all listeners that have registered interest for
// notification on this event type.  The event instance 
// is lazily created using the parameters passed into 
// the fire method.
protected void firefooXXX() {
// Guaranteed to return a non-null array
Object[] listeners = listenerList.getListenerList();
// Process the listeners last to first, notifying
// those that are interested in this event
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==FooListener.class) {
// Lazily create the event:
if (fooEvent == null)
fooEvent = new FooEvent(this);
((FooListener)listeners[i+1]).fooXXX(fooEvent);
}	       
}
}
foo should be changed to the appropriate name, and Method to the appropriate method name (one fire method should exist for each notification method in the FooListener interface).

Variable Index

o listenerList

Constructor Index

o EventListenerList()

Method Index

o add(Class, EventListener)
Add the listener as a listener of the specified type.
o getListenerCount()
Return the total number of listeners for this listenerlist
o getListenerCount(Class)
Return the total number of listeners of the supplied type for this listenerlist.
o getListenerList()
This passes back the event listener list as an array of ListenerType - listener pairs.
o remove(Class, EventListener)
Remove the listener as a listener of the specified type.
o toString()
Return a string representation of the EventListenerList.

Variables

o listenerList 
 protected transient Object listenerList[]

Constructors

o EventListenerList 
 public EventListenerList()

Methods

o getListenerList 
 public Object[] getListenerList()
This passes back the event listener list as an array of ListenerType - listener pairs. Note that for performance reasons, this implementation passes back the actual data structure in which the listner data is stored internally! This method is guaranteed to pass back a non-null array, so that no null-checking is required in fire methods. A zero-length array of Object should be returned if there are currently no listeners. WARNING!!! Absolutely NO modification of the data contained in this array should be made -- if any such manipulation is necessary, it should be done on a copy of the array returned rather than the array itself.

o getListenerCount 
 public int getListenerCount()
Return the total number of listeners for this listenerlist

o getListenerCount 
 public int getListenerCount(Class t)
Return the total number of listeners of the supplied type for this listenerlist.

o add 
 public synchronized void add(Class t,
                              EventListener l)
Add the listener as a listener of the specified type.

Parameters:
t - the type of the listener to be added
l - the listener to be added
o remove 
 public synchronized void remove(Class t,
                                 EventListener l)
Remove the listener as a listener of the specified type.

Parameters:
t - the type of the listener to be removed
l - the listener to be removed
o toString 
 public String toString()
Return a string representation of the EventListenerList.

Overrides:
toString in class Object 
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