Horstmann Chapter 5

Change Listeners

Use standard ChangeListener interface type
public interface ChangeListener
{
void stateChanged(ChangeEvent event);
}
Invoice collects ArrayList of change listeners
When the invoice changes, it notifies all listeners:
ChangeEvent event = new ChangeEvent(this);
for (int i = 0; i < listeners.size(); i++)
{
ChangeListener listener = (ChangeListener)listeners.get(i);
listener.stateChanged(event);
}