code: protected final void fireIndexedPropertyChange(String propertyName, int index,
              Object oldValue, Object newValue) {
          PropertyChangeSupport aChangeSupport = this.changeSupport;
          if (aChangeSupport == null) {
              return;
          }
          aChangeSupport.fireIndexedPropertyChange(propertyName, index,
                  oldValue, newValue);
      }
docs: Report a bound indexed property update to any registered listeners.<p>
  
  No event is fired if old and new values are equal and non-null.
  
  @param propertyName The programmatic name of the property that was changed.
  @param index index of the property element that was changed.
  @param oldValue The old value of the property.
  @param newValue The new value of the property.
  
  @since 2.0