Exception Handling trong Kotlin (try-catch)

fun main() {
    try {
        val result = 10 / 0
        println(result)
    } catch (e: ArithmeticException) {
        println("Cannot divide by zero: ${e.message}")
    }
}

fun parseInput(input: String): Int {
    return try {
        input.toInt()
    } catch (e: NumberFormatException) {
        println("Invalid number format")
        0
    } catch (e: Exception) {
        println("Unknown error: ${e.message}")
        -1
    }
}

fun readFile(path: String): String {
    val reader = File(path).bufferedReader()
    return try {
        reader.readText()
    } catch (e: IOException) {
        "Error reading file"
    } finally {
        reader.close()
        println("Reader closed")
    }
}

fun main() {
    val input = "123"
    
    val number: Int = try {
        input.toInt()
    } catch (e: NumberFormatException) {
        0
    }
    
    println(number)  // 123
}

fun validateAge(age: Int) {
    if (age < 0) {
        throw IllegalArgumentException("Age cannot be negative")
    }
    if (age > 150) {
        throw IllegalArgumentException("Age seems unrealistic")
    }
}
 
fun main() {
    try {
        validateAge(-5)
    } catch (e: IllegalArgumentException) {
        println("Error: ${e.message}")
    }
}

class InsufficientFundsException(
    val available: Double,
    val requested: Double
) : Exception("Insufficient funds: available=$available, requested=$requested")
 
class BankAccount(private var balance: Double) {
    fun withdraw(amount: Double) {
        if (amount > balance) {
            throw InsufficientFundsException(balance, amount)
        }
        balance -= amount
    }
}

fun fail(message: String): Nothing {
    throw IllegalStateException(message)
}
 
fun main() {
    val name: String = null ?: fail("Name is required")
    // Compiler biết code sau fail() không bao giờ chạy
}

fun processUser(user: User?) {
    // Ném IllegalArgumentException nếu false
    requireNotNull(user) { "User cannot be null" }
    require(user.age >= 0) { "Age must be non-negative" }
    
    // Ném IllegalStateException nếu false
    check(user.isActive) { "User must be active" }
    
    // Ném IllegalStateException
    if (!user.isVerified) {
        error("User must be verified")
    }
}

fun main() {
    val result = runCatching {
        "hello".toInt()
    }
    
    result.onSuccess { value ->
        println("Got: $value")
    }.onFailure { exception ->
        println("Error: ${exception.message}")
    }
    
    // Hoặc
    val value = result.getOrDefault(0)
    val valueOrNull = result.getOrNull()
}