Creating a leaderboard in Java using primitive arrays

Question

I'm creating a console game in Java. And I want to keep track of the scores and names.

I've already created two arrays.

String[] PlayerNames = {"Bob", "Rick", "Jack"}; // just an example
int[] PlayerScores = {40, 20, 60}; // just an example

I want to sort their scores, but also know who the score belongs to, and then print it out like this:

 Jack      60
 Bob       40      
 Rick      20

Answer 1

Create a map with the player names as the keys and the scores as the values, then sort the map based on the values:

public static void main(String[] args) {
    Map<String, Integer> unsortedMap = new HashMap<String, Integer>();
    unsortedMap.put("Jack", 60);
    unsortedMap.put("Bob", 40);
    unsortedMap.put("Rick", 20);

    Map<String, Integer> sortedMap = sortByValue(unsortedMap);
    printMap(sortedMap);
}

private static Map<String, Integer> sortByValue(Map<String, Integer> unsortMap) {

    // 1. Convert Map to List of Map
    List<Map.Entry<String, Integer>> list =
            new LinkedList<Map.Entry<String, Integer>>(unsortMap.entrySet());

    // 2. Sort list with Collections.sort(), provide a custom Comparator
    //    Try switch the o1 o2 position for a different order
    Collections.sort(list, new Comparator<Map.Entry<String, Integer>>() {
        public int compare(Map.Entry<String, Integer> o1,
                           Map.Entry<String, Integer> o2) {
            return (o1.getValue()).compareTo(o2.getValue());
        }
    });

    // 3. Loop the sorted list and put it into a new insertion order Map LinkedHashMap
    Map<String, Integer> sortedMap = new LinkedHashMap<String, Integer>();
    for (Map.Entry<String, Integer> entry : list) {
        sortedMap.put(entry.getKey(), entry.getValue());
    }

    /*
    //classic iterator example
    for (Iterator<Map.Entry<String, Integer>> it = list.iterator(); it.hasNext(); ) {
        Map.Entry<String, Integer> entry = it.next();
        sortedMap.put(entry.getKey(), entry.getValue());
    }*/


    return sortedMap;
}

public static <K, V> void printMap(Map<K, V> map) {
    for (Map.Entry<K, V> entry : map.entrySet()) {
        System.out.println("Key : " + entry.getKey()
                + " Value : " + entry.getValue());
    }
}

Note: see https://www.mkyong.com/java/how-to-sort-a-map-in-java/ for more details.