 generally encouraged) to execute the listener methods
concurrently in separate threads.
<p>
When a listener instance invokes <code>NamingEvent.getEventContext()</code>,
it must take into account the possibility that other threads will be
working with that context concurrently.  Likewise, when a listener is
registered via <code>addNamingListener()</code>, the registering thread
must take into account the likely possibility that the service provider
will later invoke the listeners in newly-created threads.  