The TooManyListenersException Exception is used as part of
the Java Event model to annotate and implement a unicast special case of
a multicast Event Source.
The presence of a throws TooManyListenersException clause
on any given concrete implementation of the normally multicast semantic
void add < EventListenerType > () event listener
registration pattern is used to annotate that interface as implementing
a unicast Listener special case, that is, that one and only one Listener
may be registered on the particular event listener source concurrently.