//declaration section
Multimap<Location, Interconnect> interconnects;
interconnects = TreeMultimap.create(Ordering.natural(),
            Interconnect.ORDER_NATURAL_NULLCHECK);

//comparator provider
static final Ordering<Interconnect> ORDER_NATURAL_NULLCHECK = new Ordering<Interconnect>() {

    @Override
    public int compare(@Nullable final Interconnect arg0,
            @Nullable final Interconnect arg1) {
        return Ordering.natural().nullsFirst().compare(arg0, arg1);
    }
};

//and I can do kind of the following quite happily:
interconnects.put(new Location(), null);
interconnects.put(new Location(), null);
interconnects.put(new Location(), null);
interconnects.put(new Location(), new Interconnect("A"));
interconnects.put(new Location(), new Interconnect("A");