A Leap Year is a year that is evenly divisible by 4, except for years that are divisible by 100 but not by 400. This means that the year 2000 was a leap year, but 1900 was not.
This project demonstrates Clean Architecture principles in Kotlin, showcasing how to structure a simple application with proper separation of concerns.
This project follows Clean Architecture principles with clear separation of layers:
┌─────────────────────────────────────────────┐
│ Presentation Layer │
│ ┌──────────┐ ┌───────────┐ ┌─────────┐ │
│ │ View │ │ ViewModel │ │ UIState │ │
│ └──────────┘ └───────────┘ └─────────┘ │
└─────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────┐
│ Domain Layer │
│ ┌──────────┐ ┌──────────┐ ┌──────────┐ │
│ │ Use Case │ │ Entity │ │Repository│ │
│ │ │ │ (Model) │ │Interface │ │
│ └──────────┘ └──────────┘ └──────────┘ │
└─────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────┐
│ Data Layer │
│ ┌──────────────┐ ┌──────────────────────┐│
│ │ Repository │ │ Data Source ││
│ │Implementation│ │ ││
│ └──────────────┘ └──────────────────────┘│
└─────────────────────────────────────────────┘
- View: Renders UI and handles user interactions (console-based)
- ViewModel: Manages presentation logic and transforms domain data to UI state
- UIState: Represents possible UI states (Success, Error)
- Use Cases: Contains business logic (e.g.,
IsLeapYearUseCase) - Entities/Models: Core business models with validation (
Year) - Repository Interfaces: Abstractions for data access
- Repository Implementation: Concrete implementation of domain repositories
- Data Sources: Handle data retrieval (console input, API, database, etc.)
- DependencyContainer: Manages object creation and dependency injection
- Dependency Rule: Dependencies point inward. Inner layers know nothing about outer layers.
- Single Responsibility: Each class has one reason to change.
- Dependency Inversion: High-level modules don't depend on low-level modules; both depend on abstractions.
- Interface Segregation: Use focused interfaces (
YearDataSource,YearRepository).
# Compile the project
kotlinc -d out $(find src/main/kotlin -name "*.kt" -type f)
# Run the application
kotlin -classpath out com.example.leapyear.MainKtEnter favorite year: 2024
2024 is a leap year.Enter favorite year: 2023
2023 is not a leap year.The application validates input and provides meaningful error messages:
Enter favorite year: abc
Error: Invalid inputEnter favorite year: -5
Error: Year must be a positive numberThe core leap year logic is encapsulated in the domain entity:
fun isLeapYear(year: Int?): Boolean {
return if (year != null) {
(year % 4 == 0) && (year % 100 != 0 || year % 400 == 0)
} else {
false
}
}
fun main() {
print("Enter favorite year: ")
val year = readlnOrNull()?.toInt()
if (isLeapYear(year)) {
println("$year is a leap year.")
} else {
println("$year is not a leap year.")
}
}In this program, the isLeapYear() function takes a year as input and returns true if it is a leap year, and false otherwise. The function checks if the year is divisible by 4, and if it is, it checks if it is not divisible by 100 or if it is divisible by 400.
The architecture makes testing easier by allowing each layer to be tested independently:
- Unit Tests: Test use cases and domain logic in isolation
- Integration Tests: Test repository implementations with mock data sources
- UI Tests: Test view models with mock repositories
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MIT License
Copyright (c) 2024 Halil OZEL
Permission is hereby granted, free of charge, to any person obtaining a copy
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