add README.md

README.md

+# Distributed Quiz System using Java RMI
+
+A distributed quiz application built with **Java Remote Method Invocation (RMI)**. The system allows multiple students (clients) to connect to a central server, answer random questions, receive immediate feedback, and view a real-time leaderboard.
+
+##  Project Overview
+
+This project demonstrates the implementation of a distributed system where:
+- **The Server** manages the quiz logic, stores questions, tracks student scores, and persists data.
+- **The Client** connects remotely to request questions and submit answers.
+- **Callbacks** are used by the server to push updates (Leaderboard) to connected clients asynchronously.
+
+##  Features
+
+- **Client-Server Architecture:** Built using Java RMI.
+- **Randomized Questions:** Clients receive random questions from the server's pool.
+- **Real-time Feedback:** Immediate validation of answers (Correct/Wrong) with score updates.
+- **Live Leaderboard:** The server broadcasts the "Top 3 Students" to all connected clients periodically using **RMI Callbacks**.
+- **Data Persistence:** Student scores are automatically saved to a file (`scores.dat`) when the server shuts down and reloaded upon restart.
+- **Concurrent Users:** Supports multiple students playing simultaneously.
+
+##  Technologies Used
+
+- **Language:** Java (JDK 8+)
+- **Communication:** Java RMI (Remote Method Invocation)
+- **Data Structure:** `HashMap` for storing scores, `ArrayList` for questions.
+- **Persistence:** `ObjectOutputStream` (Serialization).
+
+##  Project Structure
+
+```text
+src/main/java/org/example
+├── client
+│   ├── QuizClient.java          # Main client entry point
+│   └── ClientCallbackImpl.java  # Callback implementation for server notifications
+├── server
+│   ├── QuizServer.java          # Main server entry point (Registry setup)
+│   └── QuizServiceImpl.java     # Core logic (Questions, Scoring, Persistence)
+└── shared
+    ├── IQuizService.java        # Interface for Server methods
+    └── IClientCallback.java     # Interface for Client callback methods
+```
+## How to Run
+
+### Prerequisites
+*   **Java Development Kit (JDK)** installed.
+*   An IDE (IntelliJ IDEA, Eclipse) or Terminal.
+
+### Step 1: Start the Server
+1.  Navigate to the file: `org.example.server.QuizServer`.
+2.  Run the `main` method.
+3.  The console will show:
+    ```text
+    Quiz Server is running and ready...
+    ```
+    > **Note:** The server automatically starts the RMI Registry on port `1099`.
+
+### Step 2: Start the Client(s)
+1.  Navigate to the file: `org.example.client.QuizClient`.
+2.  Run the `main` method.
+3.  Enter your **name** when prompted.
+4.  Use the menu to request questions.
+5.  *Optional: Run multiple instances of `QuizClient` to simulate multiple students.*
+
+## 💾 Data Persistence
+
+The system ensures that student progress is not lost:
+
+*   **Saving:** When the server is stopped (via `SIGINT` or the IDE's **Stop** button), a **Shutdown Hook** triggers to serialize the scores `HashMap` into a `scores.dat` file.
+*   **Loading:** Upon restarting, the server looks for `scores.dat` to restore previous scores.
+
+## 📝 Usage Example
+
+```text
+--- Menu ---
+1. Get a Random Question
+2. Exit
+Choose an option: 1
+
+❓ Question: What is 1 + 1?
+✍️ Your Answer: 2
+📝 Result: Correct Answer! (+10 points) | Total Score: 10
+
+... (After 30 seconds) ...
+
+================================
+📢 Notification from Server:
+--- Leaderboard Top 3 ---
+Ali: 50
+Sara: 30
+Ahmed: 10
+-----------------------
+================================
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