// Kotlin代码示例

// 数据类
data class User(val name: String, val age: Int, val email: String? = null)

// 扩展函数
fun String.isEmail(): Boolean = contains("@") && contains(".")

// 空安全
fun getEmailLength(user: User?): Int {
    return user?.email?.length ?: 0  // Elvis运算符处理null
}

// 协程
import kotlinx.coroutines.*

suspend fun fetchData(): String {
    delay(1000)  // 非阻塞延迟
    return "Data"
}

fun main() = runBlocking {
    val results = coroutineScope {
        val data1 = async { fetchData() }
        val data2 = async { fetchData() }
        listOf(data1.await(), data2.await())
    }
    println(results)
    
    // 使用集合函数式操作
    val numbers = listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
    val evenSquares = numbers
        .filter { it % 2 == 0 }
        .map { it * it }
    
    println(evenSquares)
    
    // 使用when表达式（类似switch但更强大）
    fun describe(x: Any) = when (x) {
        is Int -> "Integer: $x"
        is String -> "String: $x"
        else -> "Unknown type"
    }
}

// 密封类
sealed class Result<out T> {
    data class Success<T>(val data: T) : Result<T>()
    data class Error(val message: String) : Result<Nothing>()
}