Treeset and Comparator

Question

I am trying to implement a schedule using a TreeSet and a Comparator.
The TreeSet constructor receives a Comparator.
Then I start adding objects that implement an Interface called ScehdulableInterface.
All objects that implement this interface have a method:
Public Date getDate()
The Comparator compare method is defined like this:
public int compare(Object o1, Object o2) {
return ((SchedulableInterface)o1).getEndDate().compareTo(((SchedulableInterface)o2).getEndDate());
My problem is the TreeSet is not accepting objects in the same date. Is there any other Collection that accepts the Comparator interface and accepts objects with the same date ?
Thanks.
Eli

Answer 1

Of course with something like this:public int compare(Object o1, Object o2) {
   // checks for null and other error handling omitted...
   SchedulableInterface si1 = (SchedulableInterface) o1;
   SchedulableInterface si2 = (SchedulableInterface) o2;
   int endDateCompare = s1.getEndDate().compareTo(s2.getEndDate();
   if (endDateCompare == 0) {
       return s1.getSubject().compareTo(s2.getSubject());
   } else {
       return endDateCompare;