(once again sry for how this issue is presented)

Playing around with generics in Kotlin, and thought this was interesting

class Example<T>(private val source: T){
    fun test(value: T?): T? = value
}

fun <T> create() = Example(null)

If we define the class to take in a non-nullable generic type, and still pass in null,

Example(null)

then the generic resolves to

Example<Nothing?>

. If we make the generic nullable

T?

then it resolves to

Example<Nothing>

. I can't find anything online that confirms that null on a generic type returns "Nothing" and I guess it kind of make sense, but can anyone confirm as to how that happens?

what is ? for in this statement val x: String? = “foo”

I just posted this question on SO - https://stackoverflow.com/questions/57783848/kotlinmapper-to-map-sql-date-to-kotlin-date I am trying to use

KotlinMapper

to cast an SQL

Date

column to Kotlin

Date

. Would appreciate any help I can get!

I have listener defined as lambda

var listener: (()->Unit)? = null

. In kotlin I would pass it like

mCircleShape.listener = {}

but how to pass it from

Java

?

This message was deleted.

runBlocking {
        try {
            val listener = aSocket(ActorSelectorManager(<http://Dispatchers.IO|Dispatchers.IO>)).tcp().bind(InetSocketAddress(12345))
            val socket = listener.accept()
            println("client connected")
            socket.openReadChannel().readInt()
        }
        catch (ex: Throwable) {
            println("client disconnected")
        }
    }

when i connect to this and then disconnect it throws a `CancellationException`which is caused by an

IOException

. More specifically, it is thrown in

readInt()

because it's trying to read data from a closed stream. I know i can and should only catch that specific exception at that specific line, but for the example code i wrapped the entire thing in catch Throwable to make double sure it catches everything. But even though I catch it and the catch block is executed just fine the exception is still thrown into the console. why is that?

Do you think kotlin will break out from the java interop thing and become a cloud native language on its own. Maybe improving upon the memory consumption or need for jvm

however current version of kotlin 1.3. There is no expectedBy

It would be nice if IDE would know it's a conflated channel and not put the suspend arrow indicator when calling send() on it... maybe it was better a specific type than an initialization parameter

hi, has anyone of you guys made a comparison of functional aspects of Java+Vavr vs. Kotlin? What are your feelings? Or is Kotlin and Vavr complementing each other?

I'm trying to use Guice injection for my kotlin project. I'm declaring stuff like

class KotlinWebService @Inject constructor(configuration: KotlinServiceConfiguration) : WebService(configuration.webServerPort, configuration.oidcBaseUrl)

that has mostly been working as expected. The problem I have is when I try to do something to the super during the init. e.g.

init { super.setUnauthorizedUrls(setOf("/path")) }

I get

java.lang.UnsupportedOperationException

. It seems like init is happening before injection. Does anyone have any ideas?

As of very recently, running Optimize Imports in IntelliJ starts inserting imports for things like

kotlin.String

,

<http://kotlin.to|kotlin.to>

, and

kotlin.with

that should not need to be imported. Both my colleague and I are noticing this . Is it just us and is there a way to stop this madness?

If I have a java library that defines

SomeImportantApiClass.java

, is it possible to declare in java a empty

Companion

object so that Kotlin users of the library can define their extension on

fun SomeImportantApiClass.Companion.someExtension()

?

Kotlin interface to lambda? (Any Trick)

Hi folks, I'm using kotlin with intellij and gradle, and have weird problem : I can access (build+run) java.io.InputStream.readAllBytes() in the IDE, but when running the project with gradle, i'm getting an "Unresolved reference: readAllBytes" readAllBytes seems included in Java12 but not in Java1.8 ... Any quick hint ? I can provide a sample project to reproduce that ...

Has anyone else experienced issues with Kotlin/Native not deallocating NSObjects?

Kotlin Ranges: Why isn't there a

downTo

variant to exclude last item like

until

?

Why are nullable function parameters not allowed on an inline function? Eg this gives an error:

inline fun foo(block: (() -> Unit)?) {
    block?.invoke()
}

Inline parameter [...] must not be nullable. Add 'noinline' modifier to the parameter declaration or make its type not nullable

Why? Would there be a problem compiling something like that? I can't imagine why. Interestingly you can suppress this,

@Suppress("NULLABLE_INLINE_PARAMETER")

but that does't actually inline the lambda, and the IDE doesn't suggest that.

Hi! I have code like this:

fun <T> test(v: T, lambda: (T) -> Unit ) {
  lambda(v)
}

And at call site i have code :

val lambda = {v : Any -> println(v)}
test<SomeObject>(SomeObject(), lambda)

The code below wont compile, cause compiler want to have my val lambda have parameter type exact as declared in function. How should I modify my fun test declaration to allow <in Parameter> in lambda parameter?

Hi! Is there anyone interested in being a reviewer for a new Kotlin book by BPB Publications? 🙂 Please ping me privately or in this thread

when using

groupBy

, is there any nice and easy way to sort the items within the groups?

Is there any channel to ask really basic doubts amongst beginners? I have just started using Kotlin!

in java i can do:

if(x!=null && x.name.equals("name"))
{}

first evaluate if x is not null then second condition, second condition is not checked if x is null and then is false since && operator only true when all its true, must stop evaluating second condition, is this by desing? how could I do this in kotlin?

Java ExecutorService Alternative in kotlin?

EDIT: nevermind, I'm an idiot, used the setter

field

, of course he force me to initialize Why does the compiler force me to initialize a variable that is never actually read? the

get()

doesn't ever expose the actual value of

entries

but if I do not include

= null

it complain with

property must be initialized

I might be wrong but I kinda remember it didn't worked like that a couple of months ago (previous versions)

wait() notify () method in Kotlin

is Kotlin supported on GraalVM ? or can i assume it'll just work due to Java compatibility ?

is there a way to define handleStopRequest using fun? as if it was a normal extention function, but defined within the object, I couldn't figure out a way