Kotlin Programmer

?: Symbol for elvis operator is ?: The elvis operator couples with safe call operator ?. Elvis operator returns the value to it's left if value is not null, else it returns the value to it's right var foo = a ?: b Here, if a is null, b is returned. If a is not null, a is returned. Another elaborate example: var msg: String? msg = null // use elvis operator var msgLength1 = msg?.length ?: 0 // use traditional null check var msgLength2: Int if (msg != null) { msgLength2 = msg.length } else { msgLength2 = 0 } println(msgLength1) // 0 println(msgLength2) // 0 In above code snippet, calculate of msgLength1 using safe call operator and elvis operator is same as calculation of msgLength2 using traditional conditional check.