If you are using Java 6, there is a method called descendingSet().
descendingSet
public NavigableSet descendingSet()
The descending set is backed by this
set, so changes to the set are
reflected in the descending set, and
vice-versa. If either set is modified
while an iteration over either set is
in progress (except through the
iterator's own remove operation), the
results of the iteration are
undefined.
The returned set has an ordering equivalent to
Collections.reverseOrder(comparator()).
The expression
s.descendingSet().descendingSet()
returns a view of s essentially
equivalent to s.
Specified by:
descendingSet in interface NavigableSet<E>
Returns:
a reverse order view of this set
Since:
1.6