Can it be done recursively? Can I somehow create a one liner fibonacci in Kotlin? 🤔

val

is read only right?

Can I ask?

There are no properties in Java, so it’s impossible there. You can have private getter and public setter methods, but not properties. It’s popular feature request https://youtrack.jetbrains.com/issue/KT-14663

Abstract class VS interface with properties and default implementation which one is preferred by you and why?

to trick the compiler in allowing you to craft and expression that's always

false

Any way to ‘fail’ the instantiation of a Kotlin class? I would like to fail instantiation in case certain constructor parameters are not valid.

Sorry, I dont speake English

In my experience,

as?

or

as

doesn't seem to work when using them with generic

T: KClass<out Any>

. For example

someClass as T

will return

someClass

, even when

T

is not `someClass`'s ancestor. if anyone could put an eye on the code in the comment to this, that would be great! Currently, in trying to achieve

instanceof

-like behavior, my method returns

true

for

Nothing::class instanceof Number::class

and I wish I was joking 🤖 . I've been trying to figure this out for maybe 3 hours now?If I'm using generics properly, then

as

and

as?

are broken when used with generics?

that is ok, spring boot bom v2.0.0.M7 contains that version

Migrated Maven multi modules project to Kotlin and get problems with sub modules dependencies. Every submodule that use another submodule write error:

Unresolved reference: moduleName

Does anybody knows what can cause this problems?

I have questions regarding the new style guide. Is this the right channel?

A newbie question, in performance view, did kotlin coroutines perform like the iOS Grand Central Dispatch, in the same orders of magnitude?

You can also replace

player1.contains(it)

with

it in player1

.

Wonder why Gson is still using that

Unsafe

hack then

Gson is dead

Just 10 years, can it be that bad? :troll:

@jw is there a blog post may be which describes these bad things about Gson? And how they are fixed in Moshi et al? I want to get educated and may be validate our serialization design against lessons learned?

Hi guys! Hello from China. I'm new to kotlin but I want to migrate small project from java to kotlin. Thing is that annotation base code geneation is used there. That code generator is written by me and it works ok with java sources and now I want to upgrade it a bit. I want it to be able to work both with java and kotlin source. What should I start with, maybe you can suggest me articles/examples to look for?

It seems that kapt is the entry point, am I right?

Is there a way to get the

Decompile

button to change backtick names to make the java code valid?

Outer::Inner

worked for me.

I was going through Kotlin samples and tried this code.

open class A {
fun f() {
    print("A")
  }
}

interface B {
fun f() {
print("B")
}
}

class C: A(),B {
}

Now, this code doesn't compile because class 'C' extends class 'A' and implements interface 'B' and both of them have functions 'f'. So, as soon as I override 'f' function in class 'C', it throws a compilation error that 'f' cannot be overridden because 'f' is not open in class A. Now a similar set up in Java would have worked easily.

class A {
final public void f() {
System.out.println("A");
}
}

interface B {
default void f() {
System.out.println("B");
}
}

class C extends A implements B{
}

Wouldn't it be better if Kotlin also worked the same way as default method of Java interfaces work i.e pick up the default implementation only when no other implementation is available? And suppose if both class 'A' and interface 'B' are from a library, I won't be able to change the function 'f' to open. In that case it would be impossible for me to create the class 'C'. Does anybody here know what is the possible advantage of having this sort of implementation in Kotlin?

Iterable

means "has an iterator". That means every

Iterable

can be used in the

for

-

in

loop, but something does not have to implement

Iterable

to be used in the

for

-

in

loop. All that is required to do so is an

operator fun iterator(): Iterator

.

If you’re not yet familiar with Kotlin iteration semantics, I strongly recommend going through the Conventions section of the Kotlin Koans

@r4zzz4k I posted how I handle iterating in Kotlin.

Interesting. Language doesn't allow

inline + reified

in interfaces, but I still can achieve virtually the same thing with extension functions:

interface Store {
  inline fun <reified T> getValue(key: String): T // impossible, no go

  // so doing this
  fun <T> getValue(key: String, clazz: Class<T>): T // good
}

class StoreImpl : Store {
  override fun <T> getValue(key: String, clazz: Class<T>): T {
    // code
  }
}

inline fun <reified T> Store.getValue(key: String): T {
  return this.getValue(key, T::class.java)
}

fun main(args: Array<String>) {
  val i: Int = StoreImpl().getValue("hello")
}

I have this type:

List<@NotBlank String>

. Is there a way to get the Kotlin compiler to properly generate type annotation metadata in a situation like this? Right now the

@NotBlank

annotation is not visible with the Java reflection API, even with

javaParameters

option set to

true

.