code: protected void notifyObservers (final Name username, final boolean muted)
      {
          _observers.apply(new ObserverList.ObserverOp<MuteObserver>() {
              public boolean apply (MuteObserver observer) {
                  observer.muteChanged(username, muted);
                  return true;
              }
          });
      }
docs: Notify our observers of a change in the mutelist.