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Sorting a text file by date - Date looks like DD/MM/YYYY

Answer 1

A:

How big is the file? I would just read in every line, create a date object for each of the lines, and then call Collections.sort(list<myobjectwithdate>)

Date provides a comparator, so you could very easily store everything in memory, sort it, and then write it back to file.

class LineAndDate implements Comparable{
  private Date date;
  private String line;

  public int compareTo( Object other )
  {
    return date.compareTo( ((LineAndDate)other).date;
  }

}

Store a List<LineAndDate> in memory, and then you should just be able to call Collections.sort(myList) and write that.

Stefan Kendall 2010-04-12 18:19:48

Answer 2

A:

Change your dates to the desired format using SimpleDateFormat, and sort on that.

Robert Harvey 2010-04-12 18:20:08

Answer 3

+2 A:

Hey take a look at this http://stackoverflow.com/questions/740936/how-do-i-sort-records-in-a-text-file-using-java

This clubbed with changing your dates to the desired format using SimpleDateFormat in getField(String line) should get you going.

ring bearer 2010-04-12 18:24:41

I noticed that it did not allow for duplicate strings when I tried to run it, as per a note in that link you gave me said as well. Also, when I run the sort it puts it into a single line. As far as the SimpleDateFormat, I would use the MM/DD/YYYY I am assuming. Thanks for your help!

John N 2010-04-13 17:23:57

Yes, a map would not allow duplicate keys. So, you might want to change the value in map to a `List<String>` so that the code looks like (Code given just for idea-sake; Did not compile/test)`List<String> records; while((line=reader.readLine())!=null){ if(map.get(getField(line) != null) { records = map.get(getField(line)); } else { records = new ArrayList<String>(); } records.add(line); map.put(getField(line),records);}`Similarly the loop that writes records out will deal with `List` values in the map.

ring bearer 2010-04-13 19:30:39

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Sorting a text file by date - Date looks like DD/MM/YYYY

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