Question

I am developing a game for android and I save the scores in a text file of the form “100&playername1,93&playername1,1950&playername2” etc. i.e. it is totally unordered.

Now I am trying to make a high score interface and I am aware that to sort the scores I should use String.split(",") followed by String.split("&")[0] to get the scores and put these in an ArrayList and then call Collections.compare(list). However once I have done that I then have no way of finding the names associated with the score.

Could anyone help me with this please. I have tried sorting the whole string in between brackets (putting the phrase “100&playername1” into the array, but that can’t sort according to orders of magnitude. By this I mean it would put 100 ahead of 1950.

Thanks for any help!

Answer 1

Make a class called UsernameScorePair. Once you have split the scores and the usernames, put them in pairs (one for each “score&username”).

For example, this class definition could work:

public class UsernameScorePair {

    private String name;
    private int score;

    public UsernameScorePair(String name, int score) {
        this.name = name;
        this.score = score;
    }

    public String getName() {
        return name;
    }

    public int getScore() {
        return score;
    }

}

Make a class called UsernameScorePairComparator that implements Comparator.

In the compare(Object o1, Object o2) method, cast the Objects to UsernameScorePairs and compare the scores. For example:

public class UsernameScorePairComparator {

    public UsernameScorePairComparator() {
    }

    public int compare(Object o1, Object o2) {
        UsernameScorePair usp1 = (UsernameScorePair)o1;
        UsernameScorePair usp2 = (UsernameScorePair)o2;

        return usp1.getScore() - usp2.getScore();
    }
}

Then use Collections.sort like this:

Collections.sort(listofpairs, new UsernameScorePairComparator())

I don’t remember if it sorts in ascending order or descending order. If it’s ascending order, then just change return usp1.getScore() - usp2.getScore(); to return usp2.getScore() - usp1.getScore();

EDIT

A Comparator basically compares two objects. In its compareTo method, it returns a negative value if the first is less than the second, a positive one if the first is greater than the second, and zero if they are both equal.

You can implement a Comparator (as I just did) to suit your needs. Then, using that Comparator, you can use standard API methods such as Collections.sort().

I hope this works!