170417(월) - Kotlin docs (Basic Syntax)

Kotlin docs

Basic Syntax

for loop

- Iterator를 사용한 synteax

fun main(args: Array<String>) {

for (arg in args) {

print(arg)

}

}

for (i in args.indices) {

print(args[i]) {

}

- withIndex

for ((index, value) in array.withIndex()) {

print($index is $value)

}

while loop

fun main(args: Array<String>) {

var i = 0

while (i < args.size) {

pirnt(args[i++])

}

}

do {

val y = retrieveData()

} while (y != null) 

when expression

fun cases(obj: Any) {

when (obj) {

1                        -> print("One")

0, 1                     -> print("x == 0 or x == 1")

"Hello"                 -> print("Greeting")

parseInt(s)             -> print("s encodes x")

in 1..10                 -> print("x is in the range")

!in 1..10                -> print("x is outside range")

in validNumbers     -> print(x is valid")

is Long                 -> print("Long")

!is Long                -> print("Not long")

else                     -> print("Unknown")

}

}

val hasPrefix = when(x) {

is String -> x.startsWith("prefix")

else       -> false

}

ranges

if (x in 1..y-1) {

print("OK")

}

if (x !in 0..array.lastIndex) {

print("Out")

}

for (x in 1..5) {

print(x)

}

- rangeTo()

Don't Understand!

rangeTo(ClosedRange<T>)

인 것 같다.

collections

for (name in names) {

println(name)

}

if (text in names) { // name.contains(text) is called

print("Yes")

}

- lambda expressions

names   

.filter { it.startsWith("A") }

.sortedBy { it }

.map ( it.toUpperCase() }

.forEach { print(it) }