📱 Phonebook Application

A feature-rich console-based Phonebook application built using Java, OOP, Collections, and File Handling.
It allows users to manage contacts efficiently with sorting, searching, grouping, favorites, and persistent storage.

✨ Features

✅ Add new contact
✅ View all contacts (sorted A–Z)
✅ 🔠 Group contacts by first letter
✅ 🔍 Search by name
✅ 📱 Search by phone number
✅ ⭐ Mark contacts as favorite
✅ 🔁 Update contact
✅ ❌ Delete contact
✅ 📌 Indian phone number validation
✅ 💾 Data stored using file handling
✅ 🧱 Object-Oriented design
✅ 📋 Menu-driven interface

🏗️ Project Structure

PhoneBook/
│── Contact.java
│── PhoneBook.java
│── Main.java
│── contacts.dat (auto-generated)

🛠️ Technologies Used

• Java
• OOP (Encapsulation, Abstraction, Comparable)
• Collections Framework (ArrayList, TreeMap)
• File Handling (Serialization)
• Regex (for phone validation)

📱 Indian Phone Number Validation

Valid formats:

• 9876543210
• 919876543210
• +919876543210

Invalid numbers are rejected.

▶️ How to Run

1️⃣ Compile

javac *.java

2️⃣ Run

java Main

📸 Sample Menu

📱 PHONEBOOK MENU
1. Add Contact
2. View All Contacts
3. Group by First Letter
4. Search by Name
5. Search by Phone
6. Mark Favorite
7. Update Contact
8. Delete Contact
9. Exit

💾 Data Storage

All contacts are saved in:

contacts.dat

So data remains available after restarting the program.