public TreeSet (Comparator<? super E> comparator)

Constructs a new, empty tree set, sorted according to the specified comparator. All elements inserted into the set must be mutually comparable by the specified comparator: comparator.compare(e1, e2) must not throw a ClassCastException for any elements e1 and e2 in the set. If the user attempts to add an element to the set that violates this constraint, the add call will throw a ClassCastException.

Parameters:
comparator    the comparator that will be used to order this set. If null, the natural of the elements will be used.