URL Shortener – Java Console Application

📌 Project Description

A Java-based URL Shortener application that converts long URLs into short URLs and retrieves the original URLs efficiently. The project uses HashMap for constant-time lookups and includes input validation, duplicate handling, and a menu-driven console interface.

This project demonstrates strong fundamentals in Data Structures, Java, and problem-solvings.

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✨ Features

• Shortens long URLs into compact short URLs
• Retrieves original URLs from short URLs
• Handles duplicate URLs by returning the same short URL
• Validates input URLs using Java’s built-in URL class
• Menu-driven console interface
• Handles empty, invalid, and incorrect inputs gracefully

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🛠 Technologies Used

• Java
• HashMap
• Java Collections Framework
• Object-Oriented Programming (OOP)
• java.net.URL

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⚙️ How It Works

1. User selects an option from the menu.
2. For URL shortening:
   • The input URL is validated.
   • A unique 6-character alphanumeric code is generated.
   • The short URL is stored using HashMap.
3. For retrieving original URL:
   • The short URL is validated.
   • The original URL is fetched using the short code.
4. All operations run in constant time on average.

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📦 Data Structures Used

• HashMap
  • shortCode → original URL
  • original URL → shortCode

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⏱ Time & Space Complexity

• Shorten URL: O(1) average time
• Retrieve Original URL: O(1) average time
• Space Complexity: O(n), where n is the number of stored URLs

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🧪 Sample Output

***** MENU *****
1. Shorten URL
2. Get Original URL
3. Exit
Enter your choice :
1
Enter the URL to shorten :
https://www.google.com
Short URL : http://short.ly/DMni3a

***** MENU *****
1. Shorten URL
2. Get Original URL
3. Exit
Enter your choice :
2
Enter short URL :
http://short.ly/DMni3a
Original URL : https://www.google.com

***** MENU *****
1. Shorten URL
2. Get Original URL
3. Exit
Enter your choice :
3
Thank you for using URL Shortener!

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▶️ How to Run

1. Clone the repository:git clone
2. Compile the Java files:javac Main.java
3. Run the application:java Main
4. Use the menu to shorten and retrieve URLs.

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📘 Key Learnings

• Understood how HashMap enables O(1) average-time lookups for fast data retrieval
• Learned the importance of bidirectional mapping for efficient reverse lookups
• Gained hands-on experience in handling duplicate data without redundancy
• Implemented input validation to handle invalid, empty, and incorrect user inputs
• Used Java’s built-in URL class to validate real-world URL formats
• Improved understanding of clean code practices and meaningful code documentation
• Built a menu-driven console application using Java control flow constructs

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🌍 Real-World Use Cases

• URL shortening services (e.g., link sharing platforms)
• Tracking and managing shortened links in marketing campaigns
• Reducing long URLs for social media and messaging platforms
• Backend services requiring fast lookup and redirection mechanisms
• Learning foundation for designing scalable web services