I am trying to call Comparator.comparingLong with kotlin lambda syntax and I get the error: Calls to static methods in Java interfaces are prohibited in JVM target 1.6. Recompile with '-jvm-target 1.8' maven kotlin My IntelliJ Project Structure says to compile for platform JVM 1.8, my Settings in IntelliJ say for the Kotlin Compiler to use target 1.8, and maven has the following in the properties tag:

<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>

I don't understand why I get this error. If anyone has insight or a fix please share!

Just wondering, if there's sealed interfaces, what are the use cases for sealed classes now?

I am trying to set

allWarningsAsErrors = true

for all my modules regardless of them being, common, multiplatform-js, multiplatform-jvm, kotlinjs, kotlin ect. Is this the right type to search for ?

subprojects {
    tasks.withType(org.jetbrains.kotlin.gradle.tasks.AbstractKotlinCompile.class) {
        kotlinOptions {
            allWarningsAsErrors = true
        }
    }
}

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Is this supposed to not work? (I'm using JVM IR)

val myNum: Int = 5
val myBigNum: Long = myNum // fine
val myMaybeBigNum: Long? = myNum // not fine

Whats the best way to write unsigned integer literals for signed types? For example I'd like to write

0xFF

and have that be converted to a signed

Byte

Hi can anyone help we with kotlin deserialization? I’m using retrofit with kotlinx serialization and I have a case where I can get 2 types of responses from the server: the first case returns a list of results with “drinks” key,

{"drinks":[{"strDrink":"Jelly Bean","strDrinkThumb":"https:\/\/<http://www.thecocktaildb.com|www.thecocktaildb.com>\/images\/media\/drink\/bglc6y1504388797.jpg","idDrink":"13775"},{"strDrink":"Turf Cocktail","strDrinkThumb":"https:\/\/<http://www.thecocktaildb.com|www.thecocktaildb.com>\/images\/media\/drink\/utypqq1441554367.jpg","idDrink":"12418"}]}

but sometimes the server returns the following:

"{"drinks":"None Found"}"

Before using kotlinx I had a custom type convertor with Gson, and that worked fine, but I’m struggling with kotlin. I tried to create a KSerializer to try to parse the result, and return an object with an empty list if an exception is thrown, but I keep getting this exception:

java.lang.IllegalStateException: Reader has not consumed the whole input: JsonReader(source='{"drinks":"None Found"}', currentPosition=22, tokenClass=1, tokenPosition=10, offset=11)

Any ideas how to solve this? I can always return a string instead of a data class, but this is ugly AF

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has someone a good tip for a kapt tutorial for serverside annotation processing? (Android is not involved in any way. The task is to generate a documentation file containing which classes contain certain annotations. Since it's Kotlin files we're talking about, I guess that kapt is the right tool for the job!?)

Can write it better ??🙂

val listType = object : TypeToken<List<Cookie>>() {}.type
val encodedCookie = sharedPreferences.getString(url.host, null)
val cookies: List<Cookie>? = encodedCookie?.run { gson.fromJson(encodedCookie, listType) }
return cookies ?: ArrayList()

Yea, we are starting the 1.5.0 release activities. Please be patient, it will take a bit of time. It will be officially out only after the blog post appears in blog.jetbrains.com/kotlin. 🙂

Why is this not a compile time error? Was this always like this? I'd expect this to be a regular type mismatch compile error

is there a channel I can post a job offer?

I've stumbled upon an old kotlin channel on gitter recently and couldn't help but wonder why you've moved away from it to slack? Gitter messages seem to be google'able in addition to being open for all. Just curious is all. Would help a ton in persisting valuable information exchanged here.

What on earth am I doing wrong? Is this not how you use

@OptIn

?

Anybody gettting this after migrating to 1.5.0?

e: org.jetbrains.kotlin.backend.common.BackendException: Backend Internal error: Exception during psi2ir
File being compiled: C:/Users/ursus/AndroidStudioProjects/o2-selfcare-android/complex-syncer/contract/src/main/java/sk/o2/complex/Mappers.kt
The root cause java.lang.NullPointerException was thrown at: org.jetbrains.kotlin.psi2ir.generators.BodyGenerator.generateSuperConstructorCall(BodyGenerator.kt:242)
	at org.jetbrains.kotlin.backend.common.CodegenUtil.reportBackendException(CodegenUtil.kt:239)
	at org.jetbrains.kotlin.backend.common.CodegenUtil.reportBackendException$default(CodegenUtil.kt:235)
	at org.jetbrains.kotlin.psi2ir.generators.DeclarationGenerator.generateMemberDeclaration(DeclarationGenerator.kt:78)
	at org.jetbrains.kotlin.psi2ir.generators.ModuleGenerator.generateSingleFile(ModuleGenerator.kt:83)
	at org.jetbrains.kotlin.psi2ir.generators.ModuleGenerator.generateModuleFragment(ModuleGenerator.kt:50)
	at org.jetbrains.kotlin.psi2ir.Psi2IrTranslator.generateModuleFragment(Psi2IrTranslator.kt:81)
	at org.jetbrains.kotlin.backend.jvm.JvmIrCodegenFactory.convertToIr(JvmIrCodegenFactory.kt:140)
	at org.jetbrains.kotlin.backend.jvm.JvmIrCodegenFactory.convertToIr$default(JvmIrCodegenFactory.kt:66)
	at org.jetbrains.kotlin.backend.jvm.JvmIrCodegenFactory.generateModule(JvmIrCodegenFactory.kt:61)
	at org.jetbrains.kotlin.codegen.KotlinCodegenFacade.compileCorrectFiles(KotlinCodegenFacade.java:35)
	at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.generate(KotlinToJVMBytecodeCompiler.kt:592)
	at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.compileModules$cli(KotlinToJVMBytecodeCompiler.kt:212)
	at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.compileModules$cli$default(KotlinToJVMBytecodeCompiler.kt:155)
	at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:169)
	at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:52)
	at org.jetbrains.kotlin.cli.common.CLICompiler.execImpl(CLICompiler.kt:88)
	at org.jetbrains.kotlin.cli.common.CLICompiler.execImpl(CLICompiler.kt:44)
	at org.jetbrains.kotlin.cli.common.CLITool.exec(CLITool.kt:98)
	at org.jetbrains.kotlin.incremental.IncrementalJvmCompilerRunner.runCompiler(IncrementalJvmCompilerRunner.kt:386)
	at org.jetbrains.kotlin.incremental.IncrementalJvmCompilerRunner.runCompiler(IncrementalJvmCompilerRunner.kt:110)

Hi Devs, kindly guide me, how to decrease the size of apk file ?

While converting legacy Java code to Kotlin, I encountered this unpleasant effect: https://pl.kotl.in/-aERlNLZ0

data class A(var b: B? = null)
data class B(var a: A? = null)

fun main() {
   val a = A()
   val b = B(a).also { a.b = it }
   println(a) // produces StackOverflow as the two toString impls call each other indefinitely
}

I suppose this is unavoidable - nevertheless, it can kill an application merely by converting a plain Java class into a data class. Any thoughts?

I like how data class auto generate copy function with optional parameters to change any field on copy. It will be very good if such possibility will appear in non data classes, for example annotated with some annotation.

wait, what? https://search.maven.org/artifact/org.jetbrains.kotlin/kotlin-bom/1.5.0/pom kotlin 1.5 was sneaky released yesterday or did I just miss the announcements? also no tag https://github.com/JetBrains/kotlin yet 🤔

Is there a way to prohibit changing

latinit

properties after they've been initialized? Something in the stdlib maybe?

In Java, I can create a map using the toMap collector, like this:

Stream.of(...)
    .toMap(
        keySelector,
        valueTransform,
        (x, y) -> {
            if (x.getTimestamp().isBefore(y.getTimestamp())) return x;
            else return y;
        });

If there would be duplicate values then the third argument determines what to do about it. In Kotlin, the

associateBy

function always keeps the most recent value. Is there a way to create a map the way Java does, where I get to decide what to do with duplicates?

ie, is it possible in the super class init block get access to values that the child class has overriden?

I don't think this is possible, but I figured I would ask anyway. Is it possible to chain together multiple enum class into a builder pattern sort of deal For instance I have something like this

enum class Page {
    PAGE_1,
    PAGE_2;
}

enum class Page1Section {
    SECTION_A,
    SECTION_B
}

enum class Page2Section {
    SECTION_1,
    SECTION_2
}

With my end goal being something like

Page.PAGE_1.SECTION_A.build()

and if I selected PAGE_2 then

Page.PAGE_2.SECTION_1.build()

Maybe this would be better in sealed classes If I selected PAGE_1, if I were to type

.

then I would get the list of Page1Section's then if I click

.

again perhaps another list of items

if you are running the latest 1.5 kotlin RC, is there a need to specify stdlib-jdk8 vs stdlib?

I’m playing around with a vdom and for this I need fast access to a hash of each node, since I’m using data classes I have access to

hashCode()

already but I want to avoid having to call it as a function because during a diff of a deeply nested structure this could happen many many times, i.e. I want to memoize the call. Can I simply add a property that is initialized to

this.hashCode()

? I’ve implemented the following which seems to work (although I haven’t tested it properly yet)

sealed class Node {
    data class TextNode(val value: String) : Node() {
        override val hash = this.hashCode()
    }
    data class TagNode(val name: String, val attributes: List<Attribute>, val children: List<Node>) : Node() {
        override val hash = this.hashCode()
    }
    abstract val hash: Int
}

Has anyone built any apps with JetBrains compose yet? If so pls share GitHub. Also, what ui framework does JetBrains compose use, I heard that it does not have all the same functionality as jet pack compose but is not far off

I was not expecting

tailrec suspend

to work, but it does! Thanks to the team, that must have been a weird edge case to handle.