class Test {

    init {
        // launch background thread that processes messages from a queue which quickly calls [callback]
        // gets Null Pointer Exception on state even though intellij says that the null check is not needed.
        // if state is moved above the init block all is well.
    }

    val state = ArrayList<Int>()
    
    fun callback(data: Int) {
        state[0] = data // Null Pointer on state, hasn't been initialized yet.
    }
}