Sorting Date & Time

[Angela D'souza]

Hi,
How to sort ascending & descending order following date & time?
June 13, 2003,10:35:46 AM PDT
June 13, 2003,8:44:06 AM PDT
May 29, 2003,2:37:57 PM PDT
Can anybody give me good example?
Thanks,
Angela
[ December 06, 2003: Message edited by: Marilyn de Queiroz ]

[Maulin Vasavada]

hi Angela
i know someone would come up with how to use Comparable or Comparator things to achieve this sort but a different way i figured out in sorting date/time is as follows,
u format ur input in string form,
yyyymmdd(AM/PM)hhmmss and just compare strings. it would work.
e.g.
1. 20030323AM05:34:45
2. 20030323PM04:34:45
when u use compareTo() of string it will return the correct result right?
regards
maulin

[Maulin Vasavada]

well,
u can ignore those ":" characters and make things look more difficult to read
regards
maulin

[Angela D'souza]

Thanks. I am using similar following things you described but doesn't work.
File dst = new File(file);
DateFormat data1 = DateFormat.getDateInstance(DateFormat.LONG);
DateFormat data2 = DateFormat.getTimeInstance(DateFormat.LONG);
String date = data1.format(new java.util.Date(dst.lastModified())) + "," + data2.format(new java.util.Date(dst.lastModified()));
and I used compare method to compare date string.
Note: String date give following results:
June 12, 2003,11:34:52 AM PDT
June 13, 2003,10:35:46 AM PDT
June 12, 2003,2:36:02 PM PDT
June 13, 2003,10:43:42 AM PDT
May 29, 2003,3:08:34 PM PDT
Please let me know
Thanks again,
Angela

[Maulin Vasavada]

hi Angela
can u please S.O.P. the output of ,
String date = data1.format(new java.util.Date(dst.lastModified())) + "," + data2.format(new java.util.Date(dst.lastModified()));
see what is the string that u get in 'date' variable and print all of them to make sure it is exactly the format what i refer to...
please note that i use "mm" as "number" in the date format meaning it can be [01..12] rather than [Jan..Dec] text based months..
regards
maulin

[Angela D'souza]

Originally posted by Maulin Vasavada:
hi Angela
see what is the string that u get in 'date' variable and print all of them to make sure it is exactly the format what i refer to...
please note that i use "mm" as "number" in the date format meaning it can be [01..12] rather than [Jan..Dec] text based months..
regards
maulin

I get following print out of 'date' variable:
June 12, 2003,11:34:52 AM PDT
June 13, 2003,10:35:46 AM PDT
June 12, 2003,2:36:02 PM PDT
June 13, 2003,10:43:42 AM PDT
May 29, 2003,3:08:34 PM PDT
How can I get the format you refer to ?
Thanks,
Angela

[Angela D'souza]

Originally posted by Maulin Vasavada:
hi Angela
please note that i use "mm" as "number" in the date format meaning it can be [01..12] rather than [Jan..Dec] text based months..
regards
maulin

what did you use to "mm" as "number" rather than text. Did you use DateFormat class???
Thanks,
Angela

[Maulin Vasavada]

hi angela
sorry about not being clear.
i didn't use any code so far i just mentioned the mechanism that works. i see in the output you have that it is not as per what i mentioned.
i suggested to have format,
yyyymmdd(AM/PM)hhmmss and i also provided the examples of that format like,
20030324AM092434
20030324PM092434
somehow get ur date in that format.
i'm sorry that i can't come up with the example right now to have that format but i 'd try once i reach home (i'm at office).
regards
maulin

[Maulin Vasavada]

hi Angela
okay..i couldn't wait till reaching home..
here u go..

import java.util.*;
import java.text.*;
public class df {
        public static void main(String[] s) {
                SimpleDateFormat sdf = new SimpleDateFormat("yyyymmddahhmmss");
                Date d = new Date();
                System.out.println(sdf.format(d));
        }
}

u get it?
to know why i have yyyymmddahhmmss as formatter please refer to the java.text.SimpleDateFormat API where they define meaning of everything..
regards
maulin

[Angela D'souza]

I tried following to get the format you suggested:
SimpleDateFormat sdf = new SimpleDateFormat("yyyymmddhhmmssa");
It gives the format you suggested in String date.
I could able to sort it out correctly. After sorting, Now I can't display like:
20030324AM092434 to the users.
Do you know how to convert this string(20030324AM092434) into following format
20003/03/24, 09:24:34 AM PST
Thanks,
Angela

[Joel McNary]

I've just seen the topic here, so I may be coming at it from a different angle, but it seems to me that the best way to sort dates (so long as you want "natural" ordering, and nothing I see in you post suggests otherwise) is to simply sort on the .getTime() method of the dates. Since Date implements Comperable, you can simply put the dates into a java.util.Date[] dateArray and call java.util.Arrays.sort(dateArray).
For a descending sort, either write a Comperator that inverts the sort criterea or, more simply, dread the array from back to front.

To answer your other question, use two SimpleDateFormats. One to convert your string to a date and then one to convert the date back to a differntly-formatted string.

[Angela D'souza]

I just used following code:
File dst = new File(fileName);
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy, HH:mm:ss a z");
String date = sdf.format(new java.util.Date(dst.lastModified()));
Then using comparator I did sorting.
It's working fine!
Thanks for help,
Angela