3강으로 끝나는 코틀린 안드로이드 개발 섹션 0

개발환경

android studio

 

 

1. 함수

//1.함수
fun main(){
hello()
println(add(a:4,b:5)

}

fun hello(): Unit{

println("hello world")


}
fun add (a : Int , b: Int) : Int{

return a+b }

 

 

2. val vs var

 

2. val vs var

fun hi() {

val a: Int = 10
var b: Int = 9

//a=100 <안됨>

b = 100

val c = 10
var d = 100 //타입 명시 안해도 됨

var name= "joice"




}

 

 

3. string 템플릿

 

fun main() {
//3. String Template

val name = "joice"
val lastName = "hong"
println("my nanme is ${name + lastName}") //변수 추출

println("this is 2\$a")

}

 

 

4. 조건식

 

fun maxBy( a: Int, b : Int) : Int{

if (a> b){

return a
} else{
return b }}

fun maxBy2( a: Int, b :Int) : Int = if(a>b) a else b

fun checkNum(score : Int) {


when(score) {
0-> println("this is 0")
1-> println("this is 1")
else ->println("NO")
}

var b :Int = when(score){

1->1
2->2
else->3}

when (score){

in 90...100 -> println("good")
else -> println("okay")




}

 

 

5. Array and List

 

 

//array 메모리 할당 필요

//list ( list , mutablelist)

fun array() {
	val array : Array<Int> = arrayOf(1,2,3)
    val list:List<Int> = listOf(1,2,3)
    
    val array2 : Array<Any> = arrayOf(1,"d",3.4f)
    cal list2 : List<Any> = listOf(1,"d",11l)
    
    array[0] = 3
    var result : Int = list.get(0)
    
    val arrayList:ArrayList<Int> = arrayListOf<Int>()
    arrayList.add(10)
    arrayList.add(20)

 

 

6. for / while

fun forAndwhile(){
val students:ArrayList<String> = arrayListOf("a","b","c")

	for( name : String in students){
    println("$(name))
}

var sum : Int = 0
for (i :Int in 1.. 10){

sum += i 
}
println(sum)

}