How to sort Java ArrayList

Question

Ive got a file called HighScores.txt which contains player names and number of points:

name1 2
name2 5
name3 1
name4 23
name5 51

And heres my code that reads the contents of this file, splitting each line and appending it to the ArrayList highScores:

public class fileHandling {

    static ArrayList highScores = new ArrayList();


    public static void readFile(String[] args) throws Exception {

        File file = new File(fileHandling.class.getClassLoader()
                .getResource("HighScores.txt").getPath());

        Scanner read = new Scanner(file);

        while (read.hasNextLine()) {
            String line = read.nextLine();
            String[] result = line.split("\\s+");
            highScores.add(Arrays.toString(result));
            System.out.println(highScores);

        }
    }

}

How do i then sort this ArrayList by the number of points each player has?

i.e. so the new array list will be:

[[name5, 51], [name4, 23], [name2, 5], [name1, 2], [name3, 1]]

Answer 1

You can create a separate object for every line in your file and then use Comparable or Comparator interface to sort these objects. Then use Collections.sort(arrayList,sorter). You can find a good tutorial here to sort user defined objects.

The class for the same can be

public class Player{
     private String name;
     private Integer score;

     //getters and setters here
}

Then create a sorter for Player objects as follows.

public class ScoreSort implements Comparator<Player>{
    public int compareTo(Player first, Player second){
            // implement sorting logic here

    }
}

Then use Collections.sort(playerList, new ScoreSort()). You can find a good tutorial at following link

http://www.thejavageek.com/2013/06/17/sorting-user-defined-objects-part-2/

Answer 2

Create a class with 2 member variable name and score. Create a new instance of class for each entry in file and store it in ArrayList. Now this class should also implement Comparable interface which compares based on score. Now use Collections.sort