💱 Currency Converter (Java)

A Java console application that allows currency conversion between several currencies using real-time exchange rates. The project follows clean architecture principles with a modular and extensible design.

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🚀 Features

• Convert between:
  • USD ↔ MXN
  • EUR ↔ MXN
  • CAD ↔ MXN
• Interactive console menu
• User input validation
• Real-time currency exchange rate retrieval via API
• Modular architecture: separation of model, business logic, and UI
• Clean and maintainable codebase

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📁 Project Structure

dev.ghector6.currencyconverter/
├── app/
│   └── Main.java                # Entry point of the application
│
├── model/
│   ├── Currency.java            # Currency rate data model
│   └── ConversionOption.java    # Enum for conversion options
│
├── service/
│   ├── CurrencyConversion.java  # Business logic for conversions
│   └── CurrencyQuery.java       # Retrieves exchange rates from API
│
└── ui/
    └── ConsoleUI.java           # Console-based user interface

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🛠️ Requirements

• Java 17 or later
• An IDE (IntelliJ IDEA, Eclipse, VS Code, etc.)
• (Optional) Gradle or Maven for build automation

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▶️ How to Run

1. Clone the repository:

git clone https://github.com/yourusername/currency-converter-java.git
cd currency-converter-java

2. Open the project in your preferred IDE and compile it.

3. Run the Main.java class located in dev.ghector6.currencyconverter.app.

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🔄 Example Usage

*******************************
Welcome to Currency Converter
1) USD => MXN
2) MXN => USD
3) EUR => MXN
4) MXN => EUR
5) CAD => MXN
6) MXN => CAD
7) Exit
*******************************
Select an option: 1
Enter amount to convert: 100
Result: 1700.00 MXN

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🌐 API Management

This application retrieves live currency exchange rates from ExchangeRate API using Java's HttpClient.

• Endpoint used:

  https://v6.exchangerate-api.com/v6/YOUR_API_KEY/latest/USD
  

• How it works:

  • A GET request is made using HttpClient.
  • The JSON response is parsed into a Currency object using the Gson library with the LOWER_CASE_WITH_UNDERSCORES naming policy.
  • This ensures accurate mapping between the API's JSON and your Java model.

• Error Handling:

  • If the API call fails (due to connection issues or an invalid key), the app throws a RuntimeException. In the future, this could be improved with user-friendly error messages or fallback data.

• Important:

  • Replace the demo API key with your own. You can get one for free by signing up at exchangerate-api.com.

URI uri = URI.create("https://v6.exchangerate-api.com/v6/YOUR_API_KEY/latest/USD");

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🧱 Design Principles

• Single Responsibility Principle (SRP)
• Safe and clean user input handling
• Object-Oriented Programming (OOP)
• Enum-based conversion modeling
• Real-world API integration

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📌 Future Improvements

• Robust API error handling and retries
• Fallback to cached or default rates on failure
• Support for more currencies and base rates
• GUI version using JavaFX or Swing
• Automated tests

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🧑‍💻 Author

• Ghector6
  GitHub

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📄 License