If I define in Kotlin List lt Int gt in java is expecting Li kotlinlang #announcements

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Title

j

jdiaz

11/18/2017, 5:03 PM

If I define in Kotlin List<Int> in java is expecting List<? extends Integer>, what's the way of maintaining compatibility?

s

snrostov

11/18/2017, 5:11 PM

Looks like

MutableList<Int>

in kotlin is same as java

List<Int>

. Btw,

List<Int>

in java can be treated as one of this types in Kotlin: -

List<Int>

-

List<Int>?

-

List<Int?>

-

List<Int?>?

-

MutableList<Int>

-

MutableList<Int>?

-

MutableList<Int?>

-

MutableList<Int?>?

a

Andreas Sinz

11/18/2017, 6:08 PM

@jdiaz what do you mean with compatibility?

d

dragas

11/18/2017, 7:38 PM

The following in kotlin

class KTesty
{
    fun foo(bar : Int)  {   }
}

is compiled into this in java

public final class KTesty {
   public final void foo(int bar) {
   }
}

Interestingly enough, you can't pass primitive values as generics in java, as a result, when when you compile the following in kotlin

val list = ArrayList<Int>()
list.add(bar)
val result = list[0]

You get this in java

ArrayList list = new ArrayList();
list.add(bar);
Integer result = (Integer)list.get(0);

Anyways, you shouldn't worry about java -> kotlin or kotlin -> java calls, as both of them are interchangeable.

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