Overview
A Java-based telephone directory application that allows users to manage contacts with both mobile and landline numbers. The application uses a doubly linked list data structure to store and manage contact information.

Features
Contact Management

Add Contacts: Add contacts with:
Mobile number only
Landline number only
Both mobile and landline numbers

Remove Contacts: Delete contacts from the directory

Display Directory: View all contacts in alphabetical order

Contact Information
Each contact stores:
Name
Area/Location
Mobile number (optional)
Landline number (optional)
Favorite status

Search Functionality
Search by Name: Find contacts by exact name match
Search by Prefix: Find contacts whose names start with specific characters
Search by Area: Display all contacts from a specific area

Favorites Management
Add to Favorites: Mark contacts as favorites
Remove from Favorites: Unmark favorite contacts

Display Favorites: View only favorite contacts

Validation
Mobile numbers must be exactly 10 digits
Landline numbers must be exactly 8 digits