Dts x dicoding #2 memulai pemrograman kotlin

Memulai
Pemrograman
dengan Kotlin
#2
Ahmad Arif Faizin
Academy Content Writer
Dicoding Indonesia
x

Tips Trik Seputar Instalasi
- Pastikan menggunakan versi yang sama dengan yang ada di modul.
- Jika sudah pernah menginstall Java sebelumnya, install dulu versi yang lama.
- Invalidate cache/restart jika tidak bisa run EduTools.
- Disable antivirus seperti Avast.
- Jika errornya “Failed to launch checking”, coba hapus folder project dan ulangi
mengambil course.
- Pastikan koneksi lancar saat instalasi.
- Kode merah-merah? pastikan besar kecil spasi sama dengan di modul.
- Untuk pengguna 32 bit bisa mencoba install JDK lewat Azul.com

3.
Kotlin Fundamental
Tipe Data & Fungsi

Hello Kotlin!
// main function
fun main() {
println("Hello Kotlin!")
}
fungsi pertama ketika
program dijalankan
untuk memberi komentar
fungsi untuk mencetak teks
ke layar/console

println vs print
fun main() {
println("Kotlin, ")
print("is Awesome!")
}
/*
output:
Kotlin,
is Awesome
*/
fun main() {
print("Kotlin, ")
print("is Awesome!")
}
/*
output:
Kotlin, is Awesome
*/

Contoh lain
fun main() {
val name = "Arif"
print("Hello my name is ")
println(name)
print(if (true) "Always true" else "Always false")
}
/*
output:
Hello my name is Arif
Always true
*/
cetak teks ke layar
untuk membuat variabel dengan tipe data string
untuk membuat
percabangan
cetak teks ke layar dan
membuat baris baru

Cara Menulis Variabel
var namaVariabel: TipeData = isi(value)
Contoh :
var company: String = "Dicoding"
atau bisa disingkat
var company = "Dicoding"
tipe data akan
menyesuaikan dengan
isinya

var vs val
Bisa diubah nilainya
(mutable)
var company = "Dicoding"
company = "Dicoding Academy"
Tidak bisa diubah nilainya
(immutable)
val company = "Dicoding"
company = "Dicoding Academy"
//Val cannot be reassigned

Tipe Data
Char hanya satu karakter ‘A’
String kumpulan dari banyak karakter (teks) “Kotlin”
Array menyimpan banyak objek arrayOf(“Aku”, “Kamu”, “Dia”)
Numbers angka 7
Boolean hanya memiliki 2 nilai true/false

Char
Contoh :
val character: Char = 'A'
Contoh salah
val character: Char = 'ABC'
// Incorrect character literal

Char
Operator increment & decrement
fun main() {
var vocal = 'A'
println("Vocal " + vocal++)
println("Vocal " + vocal--)
println("Vocal " + vocal)
}
/*
output:
Vocal A
Vocal B
Vocal A
*/

String
Memasukkan variabel ke dalam String
Contoh :
fun main() {
val text = "Kotlin"
val firstChar = text[0]
print("First character of" + text + " is " + firstChar)
}
print("First character of $text is $firstChar") string template

String
Membuat pengecualian(escaped) di dalam String
Contoh :
val statement = "Kotlin is "Awesome!""

String
Membuat Raw String
Contoh :
fun main() {
val line = """
Line 1
Line 2
Line 3
Line 4
""".trimIndent()
print(line)
}
/*
output:
Line 1
Line 2
Line 3
Line 4
*/

Array
indeks dimulai dari 0
fun main() {
val intArray = intArrayOf(1, 3, 5, 7) // [1, 3, 5, 7]
intArray[2] = 11 // [1, 3, 11, 7]
print(intArray[2])
}
/*
Output: 11
*/
1 3 5 7
ke-0 ke-1 ke-2 ke-3

Numbers
Int (32 bit) nilai angka yang umum digunakan val intNumbers = 100
Long (64 bit) nilai angka yang besar val longNumbers = 100L
Short (16 bit) nilai angka yang kecil val shortNumber: Short = 10
Byte (8 bit) nilai angka yang sangat kecil val byteNumber = 0b11010010
Double (64 bit) nilai angka pecahan val doubleNumbers = 1.3

Functions
tanpa nilai kembalian
fun main() {
setUser("Arif", 17)
}
fun setUser(name: String, age: Int){
println("Your name is $name, and you $age years old")
}
parameter yang dikirimkan
ke dalam fungsi
untuk membuat fungsi

Functions
dengan nilai kembalian
fun main() {
val user = setUser("Arif", 17)
println(user)
}
fun setUser(name: String, age: Int): String {
return "Your name is $name, and you $age years old"
}
untuk membuat nilai
kembalian
tipe data nilai yang
dikembalikan
fun setUser(name: String, age: Int) = "Your name is $name, and you $age years old"

If Expressions
percabangan berdasarkan kondisi
val openHours = 7
val now = 20
if (now > openHours){
println("office already open")
}
val openHours = 7
val now = 20
val office: String
if (now > openHours) {
office = "Office already open"
} else {
office = "Office is closed"
}
print(office)
val openHours = 7
val now = 7
val office: String
office = if (now > 7) {
"Office already open"
} else if (now == openHours){
"Wait a minute, office will be open"
} else {
"Office is closed"
}
print(office)

Nullable Types
Contoh:
val text: String? = null
Contoh salah:
val text: String = null
// compile time error

Safe Call Operator ?.
memanggil nullable dengan aman
text?.length
val textLength = text?.length ?: 7
Elvis Operator ?:
nilai default jika objek bernilai null

4.
Control Flow
Percabangan & Perulangan

When Expression
Percabangan selain If Else
fun main() {
val value = 7
val stringOfValue = when (value) {
6 -> "value is 6"
7 -> "value is 7"
8 -> "value is 8"
else -> "value cannot be reached"
}
println(stringOfValue)
}
/*
output : value is 7
*/

When Expression
val anyType : Any = 100L
when(anyType){
is Long -> println("the value has a Long type")
is String -> println("the value has a String type")
else -> println("undefined")
}
val value = 27
val ranges = 10..50
when(value){
in ranges -> println("value is in the range")
!in ranges -> println("value is outside the range")
else -> println("value undefined")
}
val x = 11
when (x) {
10, 11 -> print("the value between 10 and 11")
11, 12 -> print("the value between 11 and 12")
}
val x = 10
when (x) {
5 + 5 -> print("the value is 10")
10 + 10 -> print("the value is 20")
}

Enumeration
fun main() {
val color: Color = Color.GREEN
when(color){
Color.RED -> print("Color is Red")
Color.BLUE -> print("Color is Blue")
Color.GREEN -> print("Color is Green")
}
}
enum class Color(val value: Int) {
RED(0xFF0000),
GREEN(0x00FF00),
BLUE(0x0000FF)
}
//output : Color is Green

While
Perulangan
fun main() {
var counter = 1
while (counter <= 5){
println("Hello, World!")
counter++
}
}
fun main() {
println("Hello World")
}
=

fun main() {
var counter = 1
counter++
}
}
cek dulu
baru jalankan
While vs Do While
fun main() {
var counter = 1
do {
counter++
} while (counter <= 7)
}
jalankan dulu
baru cek

Hati - Hati dengan infinite loop
Karena kondisi tidak terpenuhi
var value = 'A'
do {
print(value)
} while (value <= 'Z')
var i = 3
while (i > 3) {
println(i)
i--
}

val rangeInt = 1.rangeTo(10)
=
val rangeInt = 1..10
=
val rangeInt = 1 until 10
dari bawah
ke atas
rangeTo vs downTo
val downInt = 10.downTo(1)
dari atas ke bawah

For Loop
Perulangan dengan counter otomatis
fun main() {
val ranges = 1..5
for (i in ranges){
println("value is $i!")
}
}
fun main() {
var counter = 1
println("value is $counter!")
counter++
}
}
=

For Each
Perulangan dengan counter otomatis
fun main() {
val ranges = 1..5
ranges.forEach{
}
}
fun main() {
val ranges = 1..5
for (i in ranges){
}
}
=

Break & Continue
Contoh program deteksi angka ganjil sampai angka 10
fun main() {
val listNumber = 1.rangeTo(50)
for (number in listNumber) {
if (number % 2 == 0) continue
if (number > 10) break
println("$number adalah bilangan ganjil")
}
}
* % adalah modulus / sisa pembagian
misal 10 % 2 == 0, 11 % 2 = 1 , 9 % 6 = 3
/*
output:
1 adalah bilangan ganjil
*/

Lanjutkan Latihan
&
Terus Belajar!

OUR LIFE SHOULD BE JUST LIKE
MODULUS. DOESN’T MATTER WHAT VALUE
IS ENTERED, IT’S RESULT ALWAYS
POSITIVE. AND SO SHOULD BE OUR LIFE
IN EVERY SITUATION
- Pranay Neve
’’
’’

You can find me at:
● Google : Ahmad Arif Faizin
● Discord : @arifaizin
Thanks!
Any questions?

Dts x dicoding #2 memulai pemrograman kotlin

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