💱 Currency Flow

A simple and clean console-based currency converter built in Java, using real-time exchange rates provided by the ExchangeRate API.

This project was designed with a backend-oriented mindset, following industry best practices such as clean architecture, separation of concerns, external API integration, and secure configuration management.

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🚀 Features

• Convert between any two supported currencies
• Uses ISO 4217 currency codes (3-letter standard: USD, BRL, EUR, etc.)
• Real-time exchange rates via external API
• Interactive console menu
• API key securely externalized using environment variables (.env)

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🧱 Project Architecture

The application follows a layered backend architecture, commonly used in Java enterprise applications:

dev.leo.currencyflow
 ├── client       # HTTP client responsible for external API communication
 ├── dto          # Data Transfer Objects (API response mapping)
 ├── service      # Business logic and currency conversion rules
 ├── controller   # Console-based input/output handling
 ├── exception    # Custom exception classes
 └── Main.java    # Application entry point

This structure improves:

• Maintainability
• Testability
• Readability
• Separation of responsibilities

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🛠️ Technologies Used

• Java 17+ — Core language
• Maven — Dependency and build management
• OkHttp — HTTP client for external API calls
• Jackson — JSON serialization/deserialization
• ExchangeRate API — Real-time currency exchange data
• java-dotenv — Environment variable management

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🔐 API Key Configuration

For security reasons, the API key is not hardcoded.

1️⃣ Create a .env file in the project root:

EXCHANGE_API_KEY=YOUR_API_KEY_HERE

2️⃣ Make sure .env is ignored by Git:

.env

3️⃣ Get your API key from:

• ExchangeRate API website

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▶️ How to Run

Prerequisites

• Java 17+ (recommended)
• Maven

Steps

Run the Main class from your IDE.

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🖥️ Console Usage Example

━━━━━ Currency Converter ━━━━━

1 - Convert from USD ($) to another currency
2 - Convert another currency to USD ($)
3 - Convert from EUR (€) to another currency
4 - Convert another currency to EUR (€)
5 - Convert from GBP (£) to another currency
6 - Convert another currency to GBP (£)
7 - Convert between any currencies
0 - Exit

The user is prompted to enter:

• Source currency
• Target currency
• Amount

The converted value is displayed immediately.

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📄 License

This project is licensed under the MIT License.

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👤 Author

Developed by Leonardo. Feel free to explore, fork, and improve this project 🚀