I have a class overriding Exception that I converted from Java. IDEA is yelling at me about this

override fun getMessage(): String {
        return super.message
    }

It says 'getMessage' overrides nothing

Hi all. How can I create a List with initial capacity in Kotlin similar to Java? It seems the mutableListOf method only has elements parameter.

Hey guys. What is the reasoning behind using the colon (":") to call the primary constructor from a secondary constructor? In other cases the ":" colon separates the type (parameter) or return type. This seems to be a little bit inconsistent for me (as a Java dev). Any explanation for that?

I spotted a weird SO question about an inconsistency in the type system https://stackoverflow.com/q/44857715/3144601 Is it a bug or a feature? Type system gurus? @dmitry.petrov, @yole?

Hi, I wanted to ask this on the #koans channel, but it seems to be quite inactive. I’m trying to install the IntelliJ Kotlin Educational Plugin, but it does not show up when browsing the repositories. Any idea what am I doing wrong?

Is there a way to make a write-only property? Just leaving out the getter doesn't work, and having it throwing an exception isn't a compile-time error.

@karelpeeters that works. took me a while too see how in your example as im used to explicit this/self. just thinking how a golang defer would be nice in this example { defer { this.started = true}(); return !this.started } .. obv this all just trivial somewhat pointless examples as I get to grips with Kotlin conventions (or lack of them)

I'm confused about when to use extension functions. Take this example in Ktor: https://github.com/Kotlin/ktor/blob/master/ktor-core/src/org/jetbrains/ktor/http/ContentTypes.kt It contains the ContentType class, but at line 120, this extension function is right next to the class:

fun ContentType.withCharset(charset: Charset) = withParameter("charset", charset.name())

Why isn't it placed inside the class?

Just press CTRL+ALT+L every so often

after two weeks, updating everything to

1.2-M1

and now top level parameters and functions are invisible from gradle dependencies projects.. what happens? anyone experienced anything similar?

@tipsy Please post your entire code so we can see what going on.

Hello, what would be the industry solution to do mocking in Kotlin?

final by default might become a problem, but if you code against interfaces that shouldn't be a problem

I'd say: If you have to use the class from Java a builder seems to be the best idea...

I have this method:

fun click(onClick: ((v: View) -> Unit)? = null) {}

What is the correct syntax for describing

click(if (condition) null else <a lambda>)

hi guys, just i'm a beginner to kotlin progra, any one can explain what is the difference between abstract and interface in kotlin?

Hello, it’s still me. Small question I can’t seem to solve by myself. I’ve put in a project which is used as a parent by another maven project this extension function:

fun RestClientBuilder.withKotlinSupport(): RestClientBuilder {
    KotlinRestClientFactoryConfigurer.configure(this)
    return this
}

Now this class just adds the KotlinModule for Jackson. The problem is that if I build my

RestClient

with the

RestClientBuilder

on the child project, there is no way I can see

withKotlinSupport

. Could you tell me a way to identify which is the problem?

For one example, i tried to understand function as first class citizen etc, which generally still can be digested. But i do not get it when FP try to advocate people to avoid null, be null safe etc. But yet kotlin has ? To define a nullable variable. This seems to give me a conflicting measage.

is it possible to

continue

the

while

if I have something like:

while(..) {
   x?.let{ ... if(y) continue }

?

it does know the return type if you specify the lambda type explicitly, right?

@poohbar I once managed to build & run "Hello World" using javac, then I tried gradle and never looked back. Don't tell me there are people that actually compile their code manually?

Hey. Anybody can help me with java interoperability? I want to call a method with a wildcard list from java Kotlin method I want to call:

class DaClass {
  companion object {
    @JvmStatic
    fun convert(strings: Iterable<String>): List<Int> {
      return strings.map { convert(it) }
    }

    @JvmStatic
    fun convert(string: String): Int {
      return java.lang.Integer.parseInt(string)
    }
  }
}

Java-Call:

List<String> list = ImmutableList.of("1", "2");
    System.out.println(DaClass.convert(list));

    List<? extends String> listWithWildcards = ImmutableList.of("1", "2");
    System.out.println(DaClass.convert(listWithWildcards)); //Does *not* compile

No, you'd have to make a factory method then and make the constructor private, which means you also need to override

copy

. If you use

invoke

in the companion object, you can make it look like a normal constructor call though.

the Gradle project wizard seems to gen src folder if you tick the "leave empty folders" box -- don't remember the wording

@jschneider The same thing:

enum class Test {
    A, B, C
}

val a = Test.valueOf("A")

And one more thing. How to throw a generic type:

public <E extends Throwable> void foo() throws E

The problem looks like functional type is nullable, so you can’t just call it with

()

. Either check it for null, or use safe call with explicit invoke

Anyone recommend any ebooks to start off with?

would an interface with those 3 fields work for you?

Hey! I am trying to understand how the type def of

getOrElse

works.

fun foo(x: String) : () -> String  = { x + "!" }

val map = mapOf(Pair("a", 1), Pair("b", 2))
val result = map.getOrElse("x", foo("kotlin"))

I would expect a type-error here, but it happily returns a String. If I define the type of

result

it works as I would expect. Can someone help me understand the type definition of `orGetElse`:

public inline fun <K, V> Map<K, V>.getOrElse(key: K, defaultValue: () -> V): V = get(key) ?: defaultValue()