Sort ArrayList reverse without implementing any method by user?

Question

   import java.util.*;
    public class Details  {

        public static void main(String args[]){
           ArrayList<String> arraylist = new ArrayList<String>();
           arraylist.add("AA");
           arraylist.add("ZZ");
           arraylist.add("CC");
           arraylist.add("FF");


           System.out.println("Before Sorting:");
           for(String str: arraylist){
                System.out.println(str);
            }

           /* Sorting in decreasing order*/

        }
    }

Now how would I do this? Im new in this field. If this stupid then I would delete it but please help me I really need this to be answered.

Answer is here - https://stackoverflow.com/questions/16252269/how-to-sort-an-arraylist — vinS, Dec 10 '17 at 07:09

janos · Answer 1 · 2017-12-10T07:51:03.670

As of Java 8, List has a sort method that takes a Comparator parameter. The natural ordering for a list of strings is alphabetic order. To sort the items of a list in their natural order you can use Comparator.naturalOrder() as the Comparator. To sort the items of a list in the reverse of their natural order, you can use Comparator.reverseOrder().

List<String> list = Arrays.asList("AA", "ZZ", "CC", "FF");
list.sort(Comparator.reverseOrder());
System.out.println(list);

If you are on an older version of Java, though I don't see a good reason for that, then you could use Collections.sort with Collections.reverseOrder() instead:

List<String> list = Arrays.asList("AA", "ZZ", "CC", "FF");
Collections.sort(list, Collections.reverseOrder());
System.out.println(list);

Amir Azizkhani · Answer 2 · 2017-12-10T07:15:47.247

2

you can use Comparator before loop:

Collections.sort(arraylist , new Comparator<String>() {
   public int compare(String o1, String o2) {
     return o1.compareTo(o2); 
   }
});

edited Dec 10 '17 at 07:15

answered Dec 10 '17 at 07:10

Amir Azizkhani

1,662
17
30

Please consider I want the list in reverse order. – CSE B Dec 10 '17 at 07:14
you can change `o1.compareTo(o2)` to `o2.compareTo(o1)` to descending sorting. – Amir Azizkhani Dec 10 '17 at 07:16
for reverse you can use `Collections.reverse(arraylist)` – Amir Azizkhani Dec 10 '17 at 07:21

score 2 · Accepted Answer · answered Dec 10 '17 at 07:13

2

import java.util.*; public class Details {
  public static void main(String args[]){
     ArrayList<String> arraylist = new ArrayList<String>();
     arraylist.add("AA");
     arraylist.add("ZZ");
     arraylist.add("CC");
     arraylist.add("FF");


     System.out.println("Before Sorting:");
     for(String str: arraylist){
          System.out.println(str);
      }

     /* Sorting in decreasing order*/
     Collections.sort(arraylist);
     Collections.reverse(arraylist);
     for(String str: arraylist){
          System.out.println(str);
      }

  }
}

answered Dec 10 '17 at 07:13

Suvam Roy

963
1
8
19

Can you please suggest how to sort it normally? – CSE B Dec 10 '17 at 07:22
By only Collections.sort(arraylist); – Suvam Roy Dec 10 '17 at 07:23
3

`arrayList.sort(Comparator.naturalOrder().reversed())`. Both nearter and faster - doesn't require another pass to reverse. – Boris the Spider Dec 10 '17 at 07:46
I never think that way!! Thanks for sharing – Suvam Roy Dec 10 '17 at 07:52

Jacob Toomey · Answer 4 · 2017-12-10T07:14:55.147

You could do:

   import java.util.*;
public class TicTacToe  {

  public static void main(String args[]){
     ArrayList<String> arraylist = new ArrayList<String>();
     arraylist.add("AA");
     arraylist.add("ZZ");
     arraylist.add("CC");
     arraylist.add("FF");
     Collections.sort(arraylist);


     System.out.println("Before Sorting:");
     for(String str: arraylist){
          System.out.println(str);
      }
     Collections.sort(arraylist, Collections.reverseOrder());
   /* Sorted List in reverse order*/
   System.out.println("ArrayList in descending order:");
   for(String str: arraylist){
        System.out.println(str);
     }
  }
}

This will sort it alphabetically then reverse it.

Sort ArrayList reverse without implementing any method by user?

4 Answers4