* @param o2 object 2
* @return -n, 0 or +n if the date represented by the second response is less than,
* the same as or greater than the first, respectively
*/
public int compare(Object o1, Object o2) {
Response r1 = (Response)o1;
Response r2 = (Response)o2;
return r2.getDate().compareTo(r1.getDate());
}