Add a PropertyChangeListener
to the listener list.
The listener is registered for all properties.
The same listener object may be added more than once, and will be called
as many times as it is added.
If listener is null, no exception is thrown and
no action is taken.
Removes a PropertyChangeListener
from the listener list. This
removes a PropertyChangeListener that was registered for all
properties. If listener was added more than once to the same
event source, it will be notified one less time after being removed. If
listener is null, or was never added, no exception is
thrown and no action is taken.
listener - the PropertyChangeListener to be removed