C# - Remove duplicate lines from a text file

/*

Contents of the text file is read into an ArrayList (allData)

Unique reference values are then extracted from allData and populated into references (another ArrayList)

*/

static DateFormat df = new SimpleDateFormat("HH:mm:ss");

...

ArrayList latest = getLatestEntries(allData, references);

private static ArrayList getLatestEntries(ArrayList allData, ArrayList references) {

        // For each reference, save the latest entry.

        ArrayList list = new ArrayList();

        for(int i = 0; i < references.size(); i++) {

               String ref = references.get(i).toString();

               Date date = null;

               int maxValIndex = i;

               //System.out.printf("ref = %s%n", ref);

               for(int j = 0; j < allData.size(); j++) {

                       String next = allData.get(j).toString();

                       if(next.split(",")[1].equals(ref)) {

                               Date nextDate = parse(next.split(",")[0]);

                               if(date == null) {

                                      date = nextDate;

                                      maxValIndex = j;

                                      continue;

                               }

                               if(nextDate.compareTo(date) > 0) {

                                      date = nextDate;

                                      maxValIndex = j;

                               }

                       }

               }

               list.add(allData.get(maxValIndex));

        }

return list;

} // getLatestEntries

private static Date parse(String s) {

        try {

               return df.parse(s);

        } catch(ParseException e) {

               System.out.println("read error: " + e.getMessage());

               System.out.println("parse error: " + e.getMessage());

               return null;

        }

} //parse