How would I specify a sort order for my data in my ArrayList in java?

Question

I have an array that holds the ranks of playing cards: A, 2, 3, 4, 5, 6, 7, 8, 9, T, J, Q, K. (The "T" represents the 10).

I have all of these stored in an ArrayList.

For example, I have an ArrayList that represents the clubs and has all of the card ranks in it:

ArrayList<Character> clubs = new ArrayList<Character>();

If I print all of the elements in this ArrayList, they print out in the following order:

3 2 4 5 6 8 7 9 T J Q K A

I then added this to sort the collection:

Collections.sort(clubs);

With the collection sort, it prints the elements in this order:

2 3 4 5 6 7 8 9 A J K Q T

How can I make it so that it prints in this order: ?

A 2 3 4 5 6 7 8 9 T J Q K

You can look into this thejavageek.com/2013/06/17/sorting-user-defined-objects-part-2 — Prasad Kharkar
– Prasad Kharkar, Commented Sep 25, 2013 at 13:41
implement your own card class and implement comparable. have a look at stackoverflow.com/questions/3320678/… you are not the first that implemented this ;-) — Philipp Sander
– Philipp Sander, Commented Sep 25, 2013 at 13:46
Instead of a Collection use Enums for the color and value of cards. Enums are using the order in which the values are declared, so no sorting needed. — Steve Benett
– Steve Benett, Commented Sep 25, 2013 at 13:52
use a map and give key values from 1-52 to every card , thus you can identify all of it — Hussain Akhtar Wahid 'Ghouri'
– Hussain Akhtar Wahid 'Ghouri', Commented Sep 25, 2013 at 13:57
@HussainAkhtarWahid i wouldn't do that.... too much work... this is also a source for tricky bugs — Philipp Sander
– Philipp Sander, Commented Sep 25, 2013 at 14:39

cmd · Accepted Answer · 2013-09-25 13:48:52Z

1

Implement java.util.Comparator

public class CharacterComparator implements Comparator<Character> {
    public int compare(Character o1, Character o2) { 
        // ...

Then call sort

List<Character> characters = ...
Collections.sort(characters, new CharacterComparator());

answered Sep 25, 2013 at 13:48

cmd

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1 Comment

jdc987 Over a year ago

It took me a while to figure out how to use the comparator, but I got it working and it does what I want. Thanks.

Ruben Serrate · Accepted Answer · 2013-09-25 13:44:48Z

1

   Collections.sort(list, new Comparator<String>() {
        public int compare(String a, String b) {
            //write here the easy code to provide you the right order
            //return -1 if a should appear before b or 1 otherwise
        }

    });

answered Sep 25, 2013 at 13:44

Ruben Serrate

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Comments

Sajan Chandran · Accepted Answer · 2013-09-25 13:45:11Z

1

You need to implement your own comparator

public class CardComparator implements Comparator<Character>{
  public int compare(Character c1, Character c2){
   //implement your own logic for comparing.
   }
}

Once its implemented, you should invoke

Collections.sort(clubs, new CardComparator);

answered Sep 25, 2013 at 13:45

Sajan Chandran

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cyon · Accepted Answer · 2013-09-25 22:40:06Z

0

As an alternative solution to implementing your own Comparator consider using Google Guava. This library contains many helpful utility classes and functions.

It provides the class Ordering which makes this quite simple:

import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;

//explicitly state the ordering
Ordering<String> ordering = Ordering.explicit("A","1","2","K");

//create unsorted list
List<String> list = Lists.newArrayList("1","1","A","2","K","K","1","A");

System.out.println(ordering.sortedCopy(list)); //sort, but not in place

Collections.sort(list, ordering); //in place sort
System.out.println(list);

edited Sep 25, 2013 at 22:40

answered Sep 25, 2013 at 13:50

cyon

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