Kotlin Playground

Introduction to Kotlin

Create a birthday message in Kotlin

Important: A variable declared using the val keyword can only be set once. You cannot change its value later in the program.

You can declare a changeable variable with the var keyword, which you will do in a later codelab.

fun main() {
    
    val age = 5 * 365
    val name = "John"
    
    println("Happy Birthday, ${name}!")
    
    // Let's print a cake!
    println("   ,,,,,   ")
    println("   |||||   ")
    println(" =========")
    println("@@@@@@@@@@@")
    println("{~@~@~@~@~}")
    println("@@@@@@@@@@@")
    
    // This prints an empty line.
    println("")

    println("You are already ${age} days old, ${name}!")
    println("${age} days old is the very best age to celebrate!")
}

Kotlin style guide

fun main() {
    printBorder()
    println("Happy Birthday, John!")
    printBorder()
}

fun printBorder() {
    repeat(21) {
        print("=")
    }
    println()
}

Passing arguments to the function to make it more flexible.

fun main() {
    val border = "`-._,-'"
    val timesToRepeat = 4
    printBorder(border, timesToRepeat)
    println("  Happy Birthday, John!")
    printBorder(border, timesToRepeat)
}

fun printBorder(border: String, timesToRepeat: Int) {
    repeat(timesToRepeat) {
        print(border)
    }
    println()
}

fun main() {
    val age = 24
    val layers = 5
    
    printCakeCandles(age)
    
    printCakeTop(age)
    
    printCakeBottom(age, layers)
    
}

fun printCakeCandles(age: Int) {
    print(" ")
    repeat(age) {
        print(",")
    }
    println()
    print(" ")
    repeat(age) {
        print("|")
    }
    println()
}

fun printCakeTop(age: Int) {
    repeat(age + 2) {
        print("=")
    }
    println()
}

fun printCakeBottom(age: Int, layers: Int) {
    repeat(layers) {
        repeat(age + 2) {
            print("@")
        }
        println()
    }
}

Create your first Android app

Build a basic layout

Qualities of a great app

• Effective
• Efficient
• Beautiful
• Accessible