Hi, I want to use the new J2K (Java to Kotlin converter) that should have been made available by Kotlin 1.3.50 IDE plugin, but I'm not finding the

Use New J2K (experimental)

settings flag in the IDE after using the search feature with the "J2K" words. Has the actual setting been forgotten to be added/enabled for use?

Ok, I found solution by myself 🙂

Going through the Coroutines documentation (https://kotlinlang.org/docs/reference/coroutines/exception-handling.html) and I found this:

If a coroutine encounters exception other than CancellationException, it cancels its parent with that exception. This behaviour cannot be overridden and is used to provide stable coroutines hierarchies for structured concurrency.

However, you have SupervisorJob which says

A failure or cancellation of a child does not cause the supervisor job to fail and does not affect its other children.

These two seem to contradict, since SupervisorJob clearly overrides the behaviour of children cancelling their parent on failure - or am I missing something?

Let's assume I have a public extension function in a class or interface

class A {
    fun String.hello() = "hello $this"
}

Is there any simpler solution of calling this function instead of having to use

with()

?

val a = A()
"Some string".run {
    with(a) { hello() }
}

Hi. I'm trying to design a nice API around entities in a kotlin project with JPA. In a legacy project we have been plagued with

val entity =  repository.getOne(entityId)
val entityId = checkNotNull(entity.id) { "Entity id cannot be null if it is retrieved from the database" }

all over the place. In the new project first we thought of using contracts, but their restrictions make them useless for this case, so this more crude idea was born:

abstract class BaseEntity<T : Serializable> {
	/**
	 * Direct use of `_dbId` is strongly discouraged in business level code, this should only be used on the persistence
	 * level by the framework and related infrastructure code.
	 */
	@Suppress("PropertyName")
	protected abstract val _dbId: T?
	/**
	 * Accessing `id` implies that entity has been retrieved from a repository or crafted with a pre-set identifier.
	 * If this condition is not met, accessing it will generate an `IllegalStateException`.
	 */
	@get:Transient
	val id: T
		get() = checkNotNull(_dbId) { "Entity has not been saved" }
}

Any thoughts? Improvements? Maybe better alternatives? In this here case, implementation would look like:

@Entity(name = "clients")
class InfoEntity(
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	override val _dbId: Long? = null,
	@Column(name = "first_name")
	var info: String = ""
) : BaseEntity<Long>()

Every time I migrate to next Kotlin version, I have to spend many days fixing builds, code, etc in the project (every time I bump k/n version, my builds broke). Every time I migrate to next Kotlin version, somewhere during migration I start googling for better alternatives, that allow to share same performance critical code for iOS, desktop and backend platforms. Every time I actually found some new tool that could do similar things, but estimates shows that it would take at least twice more time (excluding learning time) to use new tool compared to Kotlin. Thank you very much for Kotlin, K/N and the ability to deliver solutions to multiple platforms in very short time!

i've noticed that with asynchronous programming i quickly end up making almost every function in my code

suspend

. is that a sign of bad code or is this normal? i've read somewhere that at least in C# "async everything" is pretty common but im not sure if that applies to kotlin as well

Sealed with Enum (https://antonioleiva.com/sealed-classes-kotlin/)

Would you go to

sealed class Operation(val value: Int) { class Add()...class Divide()}

or

class Operation(val type:Type, val value: Int)

where

Type

is enum?

Tomorrow the Kotlin Heroes Practice 2 is taking place. Is someone aware of boilerplate code that let's you quickly test the

main

fun with the examples provided in the problems?

This property is marked as @Transient and therefore must have an initializing expression

seems like this is no longer valid?

@Transient
lateinit var rootDir: File

this seems to only be a error on 1.3.50, worked fine on 1.3.41

is there any kind of multi-key

associate { }

function that I’m missing? I’m trying to build a map and have multiple keys associated with the objects I’m iterating over - currently I’ve got something like this:

entries.flatMap { entry ->
      (entry.aliases + entry.name).map { it to entry }
}.toMap()

which probably isn’t the most efficient approach 😬

What is the difference between using Coroutine and KotlinRx? or we could use them both?

How can I make a simple tcp socket listener? The following python code does the job

python
import socket

IP = "127.0.0.1"
PORT = 25565

sock = socket.socket(socket.AF_INET, # Internet
                     socket.SOCK_STREAM)
sock.bind((IP, PORT))
sock.listen(1)
conn, addr = sock.accept()
try:
	while True:
		data = conn.recv(1024)
		if not data: break
		print(*(hex(i)[2:].rjust(2,'0') for i in data))
finally:
	conn.close()

but I can't seem to find an easy solution in kotlin

I have the following code, and I need a lot of similar looking ones. What is the easiest way to generate these?

class Handshake (val ProtocolVersion : Int,
				 val ServerAdress : String,
				 val port : UShort,
				 val NextState : Int): Packet{



	override suspend fun sendData(channel: WriteByteChannel) {
		channel.write {
			varInt(ProtocolVersion)
			string(ServerAdress)
			uShort(port)
			varInt(NextState)
		}
	}

	


	companion object {
		fun parse(channel: ReadByteChannel) = Handshake(
			ProtocolVersion = channel.readVarInt(),
			ServerAdress = channel.readString(255),
			port = channel.readUShort(),
			NextState = channel.readVarInt()
		)
	}
}

class Human(val name: String, age: Int) {
    var age = age
        private set
    
    fun birthday() {
        //party hard
        age++
    }
}

can this be simplified somehow or is it good as is?

I have the following class:

class enum<T:Types<R>, R>(Name: String) : Types<R>(Name)

but is it possible to have the following

val p = enum<varInt>("NextState"))

// instead of

val p = enum<varInt, Int>("NextState"))

// varInt
class varInt(Name: String) : Types<Int>(Name)

What is equivalent of Java

"X-Secret"::equalsIgnoreCase

?

I see that my team mates are using

lateinit var

for things that should be downloaded first. Is it good practice? (I don’t like it)

fun main() {
    val x = Thing(42)
    when(x) {
        Thing(42) -> {
            println("foo")
        }
        else -> {
            println("bar")
        }
    }
}

inline class Thing(val value: Int)

the output is

foo

IntelliJ suggests inlining

x

, like so:

fun main() {
    when(val x = Thing(42)) {
        Thing(42) -> {
            println("foo")
        }
        else -> {
            println("bar")
        }
    }
}

inline class Thing(val value: Int)

however now it outputs

bar

. why is that?

Are there any good Kotlin/Java loggers that doesn't rely on reflection?

basically:

val list: List<Pair<String, String>> = listOf(
            "a" to null,
            "b" to "hi"
        )
            .filter {it.second != null}

Why is kotlin dsl for gradle so buggy o.o Created a fresh gradle project with kotlin dsl enabled aand opening thhe file build made intellij freeze and full of errors but still built fine

Hello everyone. Experiencing an odd problem since upgrading to Kotlin 1.3.50 in a maven project Basically, I have a folder containing .otf font files which gets copied to a different folder during runtime. The code looks as follows:

private fun copyFonts () {
        val fontsFolder = File(javaClass.getResource("../../fonts").file)
        val fontsOutput = File(options.fontOutputLocation)
        if (!fontsOutput.exists()) fontsOutput.mkdir()
        fontsFolder.copyRecursively(fontsOutput, overwrite = true) { file, exception ->
            throw IllegalStateException("Could not copy file ${file.absolutePath}. ${exception.message}")
        }
    }

However, the .otf files seem to get corrupted somehow during the copy. I've tried manually converting each file to a byte array and creating files manually, same problem. In a nutshell, the files in the original /fonts folder are around 90kB, once they've been copied over they are about 150kB and LaTeX no longer recognizes the file. If I manually copy the original font files over to the output folder, LaTeX compilation goes back to working normally. I just recently updated from Kotlin 1.3.31 to 1.3.50 - which is when the problem started. Any suggestions? Thank you! EDIT: Just tried by calling

robocopy

from inside Kotlin - same problem. However, calling robocopy from powershell copies the files correctly Also: my .otf files seem to be the only ones affected by this.

It's wrapped around a

string?.let { //... }

, if I remove this I get this warning (waiting upload...)

If I remove I get this error

Someone knows how to convert this java snippet in kotlin? https://kafka.apache.org/23/javadoc/org/apache/kafka/streams/kstream/KStream.html#process-org.apache.kafka.streams.processor.ProcessorSupplier-java.lang.String...- Specifically the part when it does

return new Processor() {...

?

I'm working on a new way to build projects using vanilla Kotlin files importing this library, with the hopes that one day it could replace Gradle. I'd really like some input from people on this. https://github.com/UnknownJoe796/kbuild

Hello! How can I cast and run a method in Kotlin as example in Java I need to do this:

it as ImageButton
 it.rotateSmoothly()

Like this:

(ImageButton) it.rotateSmoothly();