Kotlin की Best Practices

sealed class PaymentResult
// Define a data class `Approved`
data class Approved(val transactionId: String) : PaymentResult()
// Define a data class `Declined`
data class Declined(val reason: String) : PaymentResult()

// Define the function `describe` taking `result` and returning a String
fun describe(result: PaymentResult): String = when (result) {
    is Approved -> "Approved: ${result.transactionId}"
    is Declined -> "Declined: ${result.reason}"
}

// Entry point: execution of the program starts here
fun main() {
    // Print `describe(Approved("tx_123"))` to the console, with a trailing newline
    println(describe(Approved("tx_123")))
}

Login to try C/C++/Java/PHP code in the editor

fun Int.isPrime(): Boolean {
    if (this < 2) return false
    // Loop over `2 until this`, binding each item to `i`
    for (i in 2 until this) {
        if (this % i == 0) return false
    }
    // Return `true` from this function
    return true
}

// Entry point: execution of the program starts here
fun main() {
    // Declare a read-only variable `primes`, set to `(2..20).filter { it.isPrime() }`
    val primes = (2..20).filter { it.isPrime() }
    // Print `primes` to the console, with a trailing newline
    println(primes)
}

Login to try C/C++/Java/PHP code in the editor

fun describeNumber(n: Int): String {
    return if (n % 2 == 0) "even" else "odd"
    // Any code placed here would be unreachable, and the compiler would warn about it
}

fun main() {
    println(describeNumber(7))
}

Login to try C/C++/Java/PHP code in the editor

// Define the function `calculateShippingCost` taking `weightKg`, `isExpress` and returning a Double
fun calculateShippingCost(weightKg: Double, isExpress: Boolean): Double {
    // Declare a read-only variable `baseCost`, set to `weightKg * 2.0`
    val baseCost = weightKg * 2.0
    // Return `if (isExpress) baseCost * 1.5 else baseCost` from this function
    return if (isExpress) baseCost * 1.5 else baseCost
}

// Entry point: execution of the program starts here
fun main() {
    // Print "Shipping cost: ${calculateShippingCost(5.0, true)}" to the console, with a trailing newline
    println("Shipping cost: ${calculateShippingCost(5.0, true)}")
}

Login to try C/C++/Java/PHP code in the editor