Descending sorting

Question

Hi all, I encounter some sorting problems.
Whenever, i sort these two in descending order, it give the same output as ascending order. The ascending works perfectly, only the descending giving me problem.
E.g.1:  "IT1193-01" , "IT1193-02" , "IT1193-03" , "IT1193-04"
public static final Comparator moduleGroup_Comparator = new Comparator()
public int compare(Object o1, Object o2)
Person mg1 = (Person)o1;
Person mg2 = (Person)o2;
return (mg1.getModuleGroup().compareTo(mg2.getModuleGroup()));
public static final Comparator moduleGroup_Comparator_desc = new Comparator()
public int compare(Object o1, Object o2)
Person mg1 = (Person)o2;
Person mg2 = (Person)o1;
return (mg1.getModuleGroup().compareTo(mg2.getModuleGroup()));     
E.g.2: "IT0401",  "IT0402",  "IT0403",  "IT0404"
public static final Comparator tutorialGroup_Comparator = new Comparator()
          public int compare(Object o1, Object o2)
               Person tg1 = (Person)o1;
               Person tg2 = (Person)o2;
               return (tg1.getTutorialGroup().compareTo(tg2.getTutorialGroup()));
     public static final Comparator tutorialGroup_Comparator_desc = new Comparator()
          public int compare(Object o1, Object o2)
               Person tg1 = (Person)o2;
               Person tg2 = (Person)o1;
               return (tg1.getTutorialGroup().compareTo(tg2.getTutorialGroup()));
     };     I don't know where the error is. I have some other sorting as well, the rest works. Only this two give me problem. Hope u all can help. Thanks.

Answer 1

I have just found my code for a reverse comparator that chains to a forward comparator
    public class ReverseComparator implements Comparator
        public ReverseComparator(Comparator chainComparator)
            this.chainComparator = chainComparator;
        public int compare(Object left, Object right)
            return chainComparator.compare(right, left);
        private Comparator chainComparator;
    }