Update the shared interface & implement the Quiz Service in the Server

src/main/java/org/example/server/QuizServiceImpl.java

+package org.example.server;
+
+import org.example.shared.IClientCallback;
+import org.example.shared.IQuizService;
+
+import java.io.FileOutputStream;
+import java.io.FileInputStream;
+import java.io.ObjectInputStream;
+import java.io.IOException;
+import java.io.ObjectOutputStream;
+import java.rmi.RemoteException;
+import java.rmi.server.UnicastRemoteObject;
+import java.util.*;
+import java.util.stream.Collectors;
+
+public class QuizServiceImpl extends UnicastRemoteObject implements IQuizService {
+
+    private List<String> questionList;
+    private Map<String, String> questionAnswerMap;
+    private Map<String, Integer> studentScores;
+    private List<IClientCallback> connectedClients;
+
+    public QuizServiceImpl() throws RemoteException {
+        super();
+
+        studentScores = new HashMap<>();
+        connectedClients = new ArrayList<>();
+        questionList = new ArrayList<>();
+        questionAnswerMap = new HashMap<>();
+        loadScoresFromFile();
+        loadQuestions();
+
+        Timer timer = new Timer();
+        timer.scheduleAtFixedRate(new TimerTask() {
+            @Override
+            public void run() {
+                broadcastLeaderboard();
+            }
+        }, 5000, 30000);
+    }
+
+    private void loadQuestions() {
+        addQuestion("What is the capital of France?", "Paris");
+        addQuestion("What is 5 + 5?", "10");
+        addQuestion("What implies RMI?", "Remote Method Invocation");
+        addQuestion("Is Java object-oriented? (yes/no)", "yes");
+        addQuestion("Which protocol is used for web pages?", "HTTP");
+
+        addQuestion("What is 1 + 1?", "2");
+        addQuestion("What is 10 - 5?", "5");
+        addQuestion("What is 2 * 3?", "6");
+        addQuestion("Which number comes after 9?", "10");
+
+        addQuestion("How many days are in a week?", "7");
+        addQuestion("What is the name of our planet?", "Earth");
+        addQuestion("What color is a banana?", "Yellow");
+        addQuestion("What is the opposite of 'Up'?", "Down");
+        addQuestion("Which animal says Meow?", "Cat");
+
+        addQuestion("Is fire hot? (yes/no)", "yes");
+        addQuestion("Do fish live in water? (yes/no)", "yes");
+        addQuestion("Is 5 bigger than 10? (yes/no)", "no");
+
+        addQuestion("What do you use to type?", "Keyboard");
+        addQuestion("What connects your computer to the web?", "Internet");
+    }
+
+    private void addQuestion(String question, String answer) {
+        questionList.add(question);
+        questionAnswerMap.put(question, answer);
+    }
+
+    @Override
+    public synchronized void login(String name, IClientCallback clientCallback) throws RemoteException {
+        connectedClients.add(clientCallback);
+
+        studentScores.putIfAbsent(name, 0);
+
+        System.out.println("Client logged in: " + name);
+    }
+
+    @Override
+    public String getQuestion() throws RemoteException {
+        if (questionList.isEmpty()) return "No questions available.";
+
+        Random rand = new Random();
+        int index = rand.nextInt(questionList.size());
+        return questionList.get(index);
+    }
+
+    @Override
+    public synchronized String submitAnswer(String name, String questionText, String answer) throws RemoteException {
+        String correctAnswer = questionAnswerMap.get(questionText);
+
+        boolean isCorrect = false;
+        if (correctAnswer != null && correctAnswer.equalsIgnoreCase(answer.trim())) {
+            isCorrect = true;
+            int currentScore = studentScores.getOrDefault(name, 0);
+            studentScores.put(name, currentScore + 10);
+        }
+
+        int score = studentScores.getOrDefault(name, 0);
+        String feedback = isCorrect ? "Correct Answer! (+10 points)" : "Wrong Answer! The correct answer was: " + correctAnswer;
+
+        return feedback + " | Total Score: " + score;
+    }
+
+    private void broadcastLeaderboard() {
+        if (connectedClients.isEmpty() || studentScores.isEmpty()) return;
+
+        String leaderboard = studentScores.entrySet().stream()
+                .sorted(Map.Entry.<String, Integer>comparingByValue().reversed())
+                .limit(3)
+                .map(entry -> entry.getKey() + ": " + entry.getValue())
+                .collect(Collectors.joining("\n"));
+
+        String message = "--- Leaderboard Top 3 ---\n" + leaderboard + "\n-----------------------";
+
+        Iterator<IClientCallback> iterator = connectedClients.iterator();
+        while (iterator.hasNext()) {
+            IClientCallback client = iterator.next();
+            try {
+                client.onLeaderboardUpdate(message);
+            } catch (RemoteException e) {
+                iterator.remove();
+            }
+        }
+    }
+
+    public void saveScoresToFile() {
+        try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("scores.dat"))) {
+            oos.writeObject(studentScores);
+            System.out.println("Scores saved to 'scores.dat' successfully.");
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private void loadScoresFromFile() {
+        try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream("scores.dat"))) {
+            studentScores = (Map<String, Integer>) ois.readObject();
+            System.out.println("Loaded scores from previous session: " + studentScores);
+        } catch (IOException | ClassNotFoundException e) {
+            System.out.println("No previous scores found. Starting fresh.");
+        }
+    }
+}
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src/main/java/org/example/shared/IClientCallback.java

@@ -3,6 +3,7 @@ package org.example.shared;
 import java.rmi.Remote;
 import java.rmi.RemoteException;
 
+
 public interface IClientCallback extends Remote {
-    void onLeaderboardUpdate(String leaderboard) throws RemoteException;
+    void onLeaderboardUpdate(String message) throws RemoteException;
 }
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src/main/java/org/example/shared/IQuizService.java

@@ -3,11 +3,11 @@ package org.example.shared;
 import java.rmi.Remote;
 import java.rmi.RemoteException;
 
-
 public interface IQuizService extends Remote {
-    String getRandomQuestion() throws RemoteException;
-    String submitAnswer(String studentName, String answer) throws RemoteException;
 
-    // Combined authentication + callback registration
-    String authenticateStudent(String studentName, IClientCallback callback) throws RemoteException;
+    void login(String name, IClientCallback clientCallback) throws RemoteException;
+
+    String getQuestion() throws RemoteException;
+
+    String submitAnswer(String name, String questionText, String answer) throws RemoteException;
 }
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