does kotlin have its own version of `Cloneable` as i cant fi kotlinlang #announcements

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Title

Smallville7123

04/15/2019, 2:49 PM

does kotlin have its own version of

Cloneable

as i cant find it in the docs nor in the search thing at kotlinlang.org

ribesg

04/15/2019, 2:50 PM

Not sure what

Cloneable

is but every

data class

has a

copy

method

fred.deschenes

04/15/2019, 2:51 PM

you can just use the one from

java.lang

Smallville7123

04/15/2019, 2:51 PM

Clonable supposidly provides the

.clone()

method in alot of java classes

i cant access java in kotlin-native

and

kotlin.Cloneable

does not exist

fred.deschenes

04/15/2019, 2:52 PM

well java.lang.Cloneable is an empty interface anyway so just create your own I guess

karelpeeters

04/15/2019, 2:52 PM

You should try to avoid in Java too, it's a mess.

☝️ 4

Smallville7123

04/15/2019, 2:54 PM

btw, if i have

var x = 1
fun a() {
    var y = x
    y = 6
    println(x)
    println(y)
}
a()

shouldnt x be modified such that y and x have the same value?

karelpeeters

04/15/2019, 2:56 PM

No, that's not how variables work in most programming languages.

You can think of variables as boxes, and

x = y

means "take the value that's in

and put it in

too". The boxes themselves,

and

, stay independent.

Smallville7123

04/15/2019, 2:58 PM

ok, so

would obtain the value of

and not the reference to

itself?

karelpeeters

04/15/2019, 2:58 PM

Yes.

Smallville7123

04/15/2019, 2:58 PM

so to implement

clone()

i would do this?

fun clone(): LinkedList<T> {
        val tmp = LinkedList<T>()
        tmp.head = head
        return tmp
    }

if so would

fun clone(): LinkedList<T> = LinkedList<T>().head = head

also work?

karelpeeters

04/15/2019, 3:02 PM

Assignments aren't expressions in Kotlin, so the second won't work and wouldn't do what you wanted anyway.

dreamreal

04/15/2019, 3:03 PM

he doesn't understand kotlin much, unfortunately - he's been spamming other networks for weeks with the same stuff

karelpeeters

04/15/2019, 3:03 PM

The first one appears to make a shallow clone, ie. if you mutate the clone the original will change too.

Smallville7123

04/15/2019, 3:07 PM

so i would need this?

val tmp = LinkedList<T>()
        forEach { tmp.append(it!!) }
        return tmp

karelpeeters

04/15/2019, 3:08 PM

Not sure why you've got the

!!

, but yeah.

Smallville7123

04/15/2019, 3:08 PM

can lists normally accept null values as valid elements?

eg MutableList<String?>().add(null)

karelpeeters

04/15/2019, 3:10 PM

They take a type parameter

, and users can make it nullable if they want, like in your example

String?

. The list code itself doesn't need to concern itself with nullability.

Smallville7123

04/15/2019, 3:10 PM

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