They might be cached, in practice -128 to +128 are cached afaik.

can u see bit clear

can u say more clearly

Int? is boxed into an object. For values in -128 to +128 the boxed objects are cached and you will always get the same object

For values outside that range, you will get different objects.

is it correct

But there is a system propery that changes this range, too, don't rely on it.

Yes, that is the behavior I just described.

but i am getting true as a output

Kotlin compiler might optimize this to only box once.

Like I said, you should never compare boxed ints with ===

val a: Int? = 20

doesn’t use

Integer(20)

, but rather

Integer.valueOf(20)

. Like @diesieben07 said, this function returns cached objects within a defined range, hence the equality passes. But you shouldn’t rely on this behavior

how can i check object reference address of a @kingsley

You can't, you are in a managed runtime. You don't get access to raw pointers.

Something that should stay in C 😛

Couldn't you use reflection or something, though?

I mean, I personally avoid that all together, but theoretically.

println(a===b)

is there an idiomatic guide to using data classes for JPA entities?

guide, cheatsheet, article, whatever

this is for use in Spring Boot, but I suspect that shouldn’t matter…

Hi guys, new to Kotlin, why is

map[arg]

Int?

and not

Int

here?

fun main(args: Array<String>) {
    val map = mutableMapOf<String, Int>()
    val lst = mutableListOf<Int>()
    map["answer"] = 42

    for (arg in args) {
        if (arg in map) {
            lst.add(map[arg])
        }
    }
}

I think this should compile just fine, but it doesn't.

@baermitumlaut The map returns

null

if the key is not found

But I test

arg in map

just before, so the key exists.

Smart casting cannot look inside the implementation of the map object and know that the returned value will not be null after the check (not to mention that it cannot make any guarantees with regard to thread safety)

You can make an assertion, however

map[arg]!!

In this case, it should never be null since I have a map with

<String, Int>

and not

<String, Int?>

, and far as I understood it, this implementation by Kotlin should then also guarantee that get never returns null? Not the case then I guess?

Ah right, that makes sense then. Thanks!

hi everyone 🙂 I was wondering if someone could help me. I have written a little util class in kotlin, but I cannot access it from a java project. is there something i need to do my java project so that it can see the kotlin jar?

i have added the jar as a dependency (using gradle), intellij just won't recognise the import