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);
}

Constructs an EventListenerAggregate object.

Parameters:

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

 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;
}

Adds the listener to this aggregate.

 public synchronized EventListener[] getListenersCopy() 
{
        return (listenerList.length == 0) ? listenerList : (EventListener[])listenerList.clone();
}

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).

 public synchronized EventListener[] getListenersInternal() 
{
        return listenerList;
}

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).

 public synchronized boolean isEmpty() 
{
        return listenerList.length == 0;
}

Returns true if this aggregate contains no listeners, false otherwise.

 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;
}

Removes a listener that is equal to the given one from this aggregate. equals() method is used to compare listeners.

 public synchronized int size() 
{
        return listenerList.length;
}

Returns the number of lisetners in this aggregate.