코틀린 공식 홈페이지를 가보면 내용을 볼 수 있다. The !! Operator The third option is for NPE-lovers: the not-null assertion operator (!!) converts any value to a non-null type and throws an exception if the value is null. We can write b!!, and this will return a non-null value of b(e.g., a String in our example) or throw an NPE if b is null: ex) val l = b!!.length Thus, if you want an NPE, you can have it, but you ..