add files

LeaderBord.java

@@ -0,0 +1,45 @@
+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));
+        }
+
+    }
+}