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Java Comparator - Sorting Question

Hi All,

Below is a comparator that sorts numbers in ascending order starting with the smallest. I want to reverse this so that it sorts numbers in descending order, the largest number appearing first and so on.

Thanks for any help

public static Comparator myComparator = new Comparator(){

            public int compare(Object value1, Object value2) {
                  String sVal1 = ((value1Entity)value1)getValue();
                  String sVal2 = ((value1Entity)value2)getValue();

int iVal1 = 0;
int iVal2 =0;

                  try { iVal1=(int)Float.parseFloat(sVal1); }
                   catch(NumberFormatException e) { }
                  try { iVal2=(int)Float.parseFloat(sVal2); }
                   catch(NumberFormatException e) { }

              if(iVal1 == 0)
                    iVal1 = 9999;
              if(iVal2 == 0)
                    iVal2 = 9999;

                  if(iVal1<iVal2)
                        return 1;
                  else if(iVal2<iVal1)
                        return -1;
                  else //(iVal2==iVal1)
                        return 0;
            }
      };

CEHJ

Just reverse iVal1 and iVal2 in the code

laptopcomputer

ASKER

That does'nt seem to be working, where in the code do you replace ?

Thanks

CEHJ

In the if-else section

ASKER CERTIFIED SOLUTION

spoxox

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CEHJ

Once you've got the values into iValX you can just do the following in fact instead of the if-else, and give yourself a means of boolean flagging the reverseSort

return reverseSort? (iVal2 - iVal1) : (iVal1 - iVal2);

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Mick Barry

You don't need to do that. Don't complicate your comparator with reverse order, instead create a new comparator using the following

Comparator reverse = Collections.reverseComparator(myComparator);

gunacesun

All that you have to do is after running your original comparator (one that returns a list in ascending order),
do a
Collections.reverse(list);

where list is the output of the original comparator.