public void remove(Activity activity) throws InstanceNotFoundException {
		boolean found = false;
		Iterator<Activity> iter;
		Activity aux;
		iter = activities.iterator();
		while (iter.hasNext() && !found) {
			if ((aux = iter.next()).equals(activity)) {
				found = true;
				activities.remove(aux);
				Persistence.getInstance().save();
			}
		}
		if (!found) {
			throw new InstanceNotFoundException(activity, "Activity");
		}
	}