P4
Properties listeners are unreachable since there isn't the appropriate getter getListeners() on.
Consequences : it's impossible to check if the property already contains the listener that you want to add, in addition the documentatation of the method addListener specifies : "If the same listener is added more than once, then it will be notified more than once. That is, no check is made to ensure uniqueness".
Consequences : it's impossible to check if the property already contains the listener that you want to add, in addition the documentatation of the method addListener specifies : "If the same listener is added more than once, then it will be notified more than once. That is, no check is made to ensure uniqueness".