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package sun.awt;
import java.lang.reflect.Array;
import java.util.EventListener;
A class that assists in managing EventListeners of the specified type. Its instance holds an array of listeners of the same type and allows to perform the typical operations on the listeners. This class is thread-safe. Author: Alexander Gerasimov Since: 1.5
/**
* A class that assists in managing {@link java.util.EventListener}s of
* the specified type. Its instance holds an array of listeners of the same
* type and allows to perform the typical operations on the listeners.
* This class is thread-safe.
*
* @author Alexander Gerasimov
*
* @since 1.5
*/
public class EventListenerAggregate {
private EventListener[] listenerList;
Constructs an EventListenerAggregate object.
Params: - listenerClass – the type of the listeners to be managed by this object
Throws: - NullPointerException – if
listenerClass is
null - ClassCastException – if
listenerClass is not
assignable to java.util.EventListener
/**
* Constructs an <code>EventListenerAggregate</code> object.
*
* @param listenerClass the type of the listeners to be managed by this object
*
* @throws NullPointerException if <code>listenerClass</code> is
* <code>null</code>
* @throws ClassCastException if <code>listenerClass</code> is not
* assignable to <code>java.util.EventListener</code>
*/
public EventListenerAggregate(Class listenerClass) {
if (listenerClass == null) {
throw new NullPointerException("listener class is null");
}
if (!EventListener.class.isAssignableFrom(listenerClass)) {
throw new ClassCastException("listener class " + listenerClass +
" is not assignable to EventListener");
}
listenerList = (EventListener[])Array.newInstance(listenerClass, 0);
}
private Class getListenerClass() {
return listenerList.getClass().getComponentType();
}
Adds the listener to this aggregate.
Params: - listener – the listener to be added
Throws: - ClassCastException – if
listener is not
an instatce of listenerClass specified
in the constructor
/**
* Adds the listener to this aggregate.
*
* @param listener the listener to be added
*
* @throws ClassCastException if <code>listener</code> is not
* an instatce of <code>listenerClass</code> specified
* in the constructor
*/
public synchronized void add(EventListener listener) {
Class listenerClass = getListenerClass();
if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
throw new ClassCastException("listener " + listener + " is not " +
"an instance of listener class " + listenerClass);
}
EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass, listenerList.length + 1);
System.arraycopy(listenerList, 0, tmp, 0, listenerList.length);
tmp[listenerList.length] = listener;
listenerList = tmp;
}
Removes a listener that is equal to the given one from this aggregate.
equals() method is used to compare listeners.
Params: - listener – the listener to be removed
Throws: - ClassCastException – if
listener is not
an instatce of listenerClass specified
in the constructor
Returns: true if this aggregate contained the specified
listener; false otherwise
/**
* Removes a listener that is equal to the given one from this aggregate.
* <code>equals()</code> method is used to compare listeners.
*
* @param listener the listener to be removed
*
* @return <code>true</code> if this aggregate contained the specified
* <code>listener</code>; <code>false</code> otherwise
*
* @throws ClassCastException if <code>listener</code> is not
* an instatce of <code>listenerClass</code> specified
* in the constructor
*/
public synchronized boolean remove(EventListener listener) {
Class listenerClass = getListenerClass();
if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
throw new ClassCastException("listener " + listener + " is not " +
"an instance of listener class " + listenerClass);
}
for (int i = 0; i < listenerList.length; i++) {
if (listenerList[i].equals(listener)) {
EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass,
listenerList.length - 1);
System.arraycopy(listenerList, 0, tmp, 0, i);
System.arraycopy(listenerList, i + 1, tmp, i, listenerList.length - i - 1);
listenerList = tmp;
return true;
}
}
return false;
}
Returns an array of all the listeners contained in this aggregate.
The array is the data structure in which listeners are stored internally.
The runtime type of the returned array is "array of listenerClass"
(listenerClass has been specified as a parameter to
the constructor of this class).
Returns: all the listeners contained in this aggregate (an empty
array if there are no listeners)
/**
* Returns an array of all the listeners contained in this aggregate.
* The array is the data structure in which listeners are stored internally.
* The runtime type of the returned array is "array of <code>listenerClass</code>"
* (<code>listenerClass</code> has been specified as a parameter to
* the constructor of this class).
*
* @return all the listeners contained in this aggregate (an empty
* array if there are no listeners)
*/
public synchronized EventListener[] getListenersInternal() {
return listenerList;
}
Returns an array of all the listeners contained in this aggregate.
The array is a copy of the data structure in which listeners are stored
internally.
The runtime type of the returned array is "array of listenerClass"
(listenerClass has been specified as a parameter to
the constructor of this class).
Returns: a copy of all the listeners contained in this aggregate (an empty
array if there are no listeners)
/**
* Returns an array of all the listeners contained in this aggregate.
* The array is a copy of the data structure in which listeners are stored
* internally.
* The runtime type of the returned array is "array of <code>listenerClass</code>"
* (<code>listenerClass</code> has been specified as a parameter to
* the constructor of this class).
*
* @return a copy of all the listeners contained in this aggregate (an empty
* array if there are no listeners)
*/
public synchronized EventListener[] getListenersCopy() {
return (listenerList.length == 0) ? listenerList : (EventListener[])listenerList.clone();
}
Returns the number of lisetners in this aggregate.
Returns: the number of lisetners in this aggregate
/**
* Returns the number of lisetners in this aggregate.
*
* @return the number of lisetners in this aggregate
*/
public synchronized int size() {
return listenerList.length;
}
Returns true if this aggregate contains no listeners,
false otherwise.
Returns: true if this aggregate contains no listeners,
false otherwise
/**
* Returns <code>true</code> if this aggregate contains no listeners,
* <code>false</code> otherwise.
*
* @return <code>true</code> if this aggregate contains no listeners,
* <code>false</code> otherwise
*/
public synchronized boolean isEmpty() {
return listenerList.length == 0;
}
}