data class VersionCode(val code: String) {
    val major: Int
    val minor: Int
    val patch: Int
    init {
        val (first, second, third) = code.substringAfter('v').split('.')
        major = first.toInt()
        minor = second.toInt()
        patch = third.toInt()
    }
}

String

MyDataClass

MyDataClass?

null

Result

null

if (list?.isEmpty())

if (list?.isEmpty() == true)

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.0'
    }
}
repositories {
    google()
    jcenter()
}

String

Any

data class Foo(val name:String, val age:Int)        
        val sortModes = mapOf("name" to Foo::name, "age" to Foo::age)
        val myList = listOf(Foo("Dog", 17), Foo("Cat", 12), Foo("Mouse", 3))
        val sortFunc = sortModes["name"] ?: error("Not found") //  returns KProperty1<Foo, Any>
        println(myList.sortedWith(compareBy(sortFunc)) // <-- compiler error

Any

acraWrapper.logAndThrow()

Map<Class, Object>

Map<Class<Any>, Any>

Map<Class<*>, Any>

objects.name

private val typeface = Typeface.create(Typeface.DEFAULT_BOLD, Typeface.BOLD)

class InitialsDrawable(val context: Context) : Drawable() {
    private val textPaint = Paint().apply {
        isAntiAlias = true
        color = context.getAttr(R.attr.defaultTextColor)
        textSize = context.resources.dpToPixels(11F)
        typeface = @file:typeface <--------------
        textAlign = Paint.Align.CENTER
    }

while (index < 3) {  
        index ++

        val result = cakesList?.let{ 
                 if(index == 2) {
                     "HelloString"
                 } else {
                  2   
                 }
            } 

        println("result value = $result")

        when(result) {
          is String -> println(" result variable is a String")

          is Int -> println(" result variable is Integer")
}

> java.lang.NullPointerException (no error message)

v[0]!!::class.objectInstance

fun ret() {
    class a {
        var empty: Int = 0
    }

    val f = arrayListOf<a>()
    f.add(a()) // class a is explicitly specified
}