import java.util.HashMap;
import java.util.Map;
import java.util.PriorityQueue;

class Leaderboard {
    private Map<User, Integer> scores = new HashMap<>();
    private PriorityQueue<User> displayList = new PriorityQueue<>(
            (u1, u2) -> u2.getScore() - u1.getScore());

    public void addUser(User a) {
        scores.put(a, a.getScore());

    }

    static Leaderboard obj = new Leaderboard();

    private Leaderboard() {
    }

    public static Leaderboard getObject() {
        return obj;
    }

    public void updateScore(User user, int points) {
        int p = user.getScore();
        p += points;
        user.setScore(p);
        scores.put(user, p);
    }

    public void display() {
        displayList.clear();
        System.out.println();
        System.out.println("Leaderboard");
        System.out.println("--------------------------------");
        for (User u : scores.keySet()) {
            displayList.add(u);
        }
        while (!displayList.isEmpty()) {
            User u = displayList.poll();
            System.out.println(u.getUsername() + " --- " + scores.get(u));
        }

    }
}