Daily Kotlin - 라벨 in lambda, break, continue, exception, 클래스, 상속(open)

• 라벨을 이용한 return

package chap04.section3.noinline

fun main() {
    retFunc()
}

inline fun inlineLambda(a: Int, b: Int, out: (Int, Int) -> Unit) {
    out(a, b)
}

fun retFunc() {
    println("start of retFunc")
    inlineLambda(13, 3) lit@{ a, b ->
        val result = a + b
        if(result > 10) return@lit
        println("result: $result")
    }
    println("end of retFunc")
}

• 라벨을 이용한 break, continue

package chap04.section3

fun main() {
    println("Break")
    first@ for(i in 1..5) {
        second@ for(j in 1..5) {
            if(j == 3) break@first
            println("i:$i, j:$j")
        }
        println("after for j")
    }
    println("after for i")

    println("Continue")
    first@ for(i in 1..5) {
        second@ for(j in 1..5) {
            if(j == 3) continue@first
            println("i$i, j:$j")
        }
        println("after for j")
    }
    println("after for i")
}

Break
i:1, j:1
i:1, j:2
after for i
Continue
i1, j:1
i1, j:2
i2, j:1
i2, j:2
i3, j:1
i3, j:2
i4, j:1
i4, j:2
i5, j:1
i5, j:2
after for i

• try-catch

package chap04.section3

fun main() {
    var a = 6
    var b = 0
    val c: Int

    try {
        c = a / b
    } catch (e: Exception) {
        println("Exception handled ${e.message}")
        e.printStackTrace()
    } finally {
        println("finally executed")
    }
}

Exception handled / by zero
finally executed
java.lang.ArithmeticException: / by zero
	at chap04.section3.TryCatchKt.main(TryCatch.kt:9)
	at chap04.section3.TryCatchKt.main(TryCatch.kt)

• Throw Exception

package chap04.section3

fun main() {
    var amount = 600

    try {
        amount -= 100
        checkAmount(amount)
    } catch(e: Exception) {
        println(e.message)
    }
    print("amount: $amount")
}

fun checkAmount(amount: Int) {
    if(amount < 1000) {
        throw Exception("잔고가 $amount 로 1000 이하 입니다.")
    }
}

잔고가 500 로 1000 이하 입니다.
amount: 500

• Custom Exception

package chap04.section3

class InvalidNameException(message: String): Exception(message)

fun main() {
    var name = "Kildong123"
    try {
        validateName(name)
    } catch(e: Exception) {
        println(e.message)
    } 
}

fun validateName(name: String) {
    if(name.matches(Regex(".*\\d+.*"))) {
        throw InvalidNameException("Your name : $name : contains numerals")
    }
}

Your name : Kildong123 : contains numerals

• 부생성자

package chap05.section2.secondary

class Bird {
    var name: String
    var wing: Int
    var beak: String
    var color: String

    constructor(name: String, wing: Int, beak: String, color: String) {
        this.name = name
        this.wing = wing
        this.beak = beak
        this.color = color
    }

    fun fly() = println("Fly wing: $wing")
    fun sing(vol: Int) = println("Sing vol: $vol")
}

fun main() {
    val coco = Bird("mybird", 2, "short", "blue")

    coco.color = "yellow"
    println("coco.color: ${coco.color}")
    coco.fly()
    coco.sing(3)
}

• 주생성자

package chap05.section2.primary

class Bird(var name: String, var wing: Int, var beak: String, var color: String) {
    fun fly() = println("Fly wing: $wing")
    fun sing(vol: Int) = println("Sing vol: $vol")
}

fun main() {
    val coco = Bird("mybird", 2, "short", "blue")

    coco.color = "yellow"
    println("coco.color: ${coco.color}")
    coco.fly()
    coco.sing(3)
}

• 상속

open키워드를 통해 상속 가능한 클래스임을 명시

package chap05.section3.openclass

open class Bird(var name: String, var wing: Int, var beak: String, var color: String) {
    fun fly() = println("Fly wing: $wing")
    fun sing(vol: Int) = println("Sing vol: $vol")
}

class Lark(name: String, wing: Int, beak: String, color: String): Bird(name, wing, beak, color) {
    fun singHitone() = println("Happy Song!")
}

class Parrot: Bird {
    val language: String

    constructor(name: String, wing: Int, beak: String, color: String, language: String) : super(name, wing, beak, color) {
        this.language = language;
    }

    fun speak() = println("Speak! $language")
}

fun main() {
    val coco = Bird("mybird", 2, "short", "blue")
    val lark = Lark("mylark", 2, "long", "brown")
    val parrot = Parrot("myparrot", 2, "short", "multiple", "Korean")

    lark.singHitone()
    parrot.speak()
    lark.fly()
    parrot.sing(5)
    print(coco.color)
}