Sets a new handler, that will receive any events not handled by a child
of the reactor. Note that setting a handler via this method replaces
the previous handler, and will result in no further events being
dispatched to the child handlers associated with the previous handler.
For this reason it is recommended that you do not use this method and
instead add child handlers to the value returned by the
{@link #getHandler()} method.
@param handler the new handler for this reactor.
Sets a new handler, that will receive any events not handled by a child of the reactor. Note that setting a handler via this method replaces the previous handler, and will result in no further events being dispatched to the child handlers associated with the previous handler. For this reason it is recommended that you do not use this method and instead add child handlers to the value returned by the {@link #getHandler()} method. @param handler the new handler for this reactor.