data class MyDataClass(
        val myMap: Map<Int, String> = mapOf()
)

fun addElementToMyDataClass(myInstance : MyDataClass, key : Int, value : String): MyDataClass {
    val mutableCopyOfMap = myInstance.myMap.toMutableMap()
    mutableCopyOfMap[key] = value
    return myInstance.copy(myMap = mutableCopyOfMap)
}

val fullTariffList = arrayOf("customer", "reseller", "vendor").flatMap { type ->  testTariffList.map { it.copy(type = type) } }

ArrayList<Long>

when (obj) {
    null -> println("is null")
    else -> println("is not null")
}

!null ->

contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) }

contract

fun ArrayList<ItemStack>.tick(){
    var emptyStack: ItemStack
    for(stack in this){
        if(emptyStack == null) {
            if (stack.isEmpty) {
                emptyStack = stack
            }
        }
    }
}

// numberList: 1, 2, 3, 4, 5, 6

numberList.contains(1,2,6)

int("whatever") ?: default

.let .also .apply etc

Common

userRepo.getUser(userId)

set(value) { baz.bar = value }

baz

sealed class NetworkResource<out ResponseType, out ErrorType> {
    class Loading<out ResponseType, out ErrorType> : NetworkResource<ResponseType, ErrorType>()
    data class Success<out ResponseType, out ErrorType>(val response: ResponseType) : NetworkResource<ResponseType, ErrorType>()
    data class Error<out ResponseType, out ErrorType>(val error: ErrorType) : NetworkResource<ResponseType, ErrorType>()
}

class NetworkObserver<ResponseType, ErrorType> : Observer<NetworkResource<ResponseType, ErrorType>> {}

incompatible types: <anonymous NetworkObserver<Object,String>> cannot be converted to Observer<NetworkResource<Object,String>>

out

Runtime JAR files in the classpath should have the same version.