In the old days, before generics, I wrote

    private SortedSet onhand;

    Iterator getInventoryIterator() {
       return (onhand == null ? Collections.EMPTY_SET ? onhand)
           .iterator();
    }

... the idea being to create the SortedSet only if there are
actually some Inventory objects to store in it, and to return
a suitable Iterator whether or not the SortedSet exists.

    Now, in an effort to leave prehistory behind me and adopt
generics with all their benefits, I change the SortedSet to a
SortedSet<Inventory> and change the return type of the method
to Iterator<Inventory> -- but how do I rewrite the guts of the
method to get the compiler to understand that all is well?  The
problem seems to be that Collections.EMPTY_SET.iterator() returns
an Iterator<Object>, and the compiler complains when I try to
return this in place of the desired Iterator<Inventory>.  I've
tried a few variations, but have only succeeded in moving the
warning message around, not in eliminating it:

    return (onhand == null
       ? (Set<Inventory>)Collections.EMPTY_SET : onhand)
       .iterator();

    return (Iterator<Inventory>)
       (onhand == null ? Collections.EMPTY_SET ? onhand)
       .iterator();

    This seems like a lot of trouble to take over the empty set,
but there ought to be *some* clean way to do it.  Ideas?