Sorting my list

[shaf maff]

Hi Guys,

I have a list which containers mail orders from the db which are stored in a session. What Ive noticed when I view the orders on the webpage is that it starts from the oldest date to the newest. I want to switch this around. Is there any way I can do this? See basic structure of list below:

List<Mail> mymail = new ArrayList<Mail>();
Mail mail = new Mail();
mail.setDate = rs.getString("Date");
mymail.add(mail);

[arulk pillai]

use a compareTo method to sort in reverse order i.e. latest first.


implement a compareTo method in your Mail class. Make sure that it implements the Comparable interface. http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Comparable.html

 public int compareTo(Object o)
{
Mail other = (Mail) o;
return this.dateField.compareTo(other.dateField);//if you want reverse
}

You can then sort it as shown below. Your compareTo method gets called. Fopr more complex sorting, write your own Comparator. Check the Java API.

Collections.sort(mymail);

http://java.sun.com/j2se/1.4.2/docs/api/java/util/Collections.html#sort(java.util.List)

http://www.java2s.com/Tutorial/Java/0140__Collections/SortingaList.htm

[ September 25, 2008: Message edited by: arulk pillai ]

[ September 25, 2008: Message edited by: arulk pillai ]
[ September 25, 2008: Message edited by: arulk pillai ]

[Renato Losio]

Why not sorting them when you query from the DB?

[Bosun Bello]

This type of sorting is best done via your SQL when you do your select.