``` val a = 5 val b = 5 4 val c = 5 4321 ``` kotlinlang #getting-started

08/21/2018, 3:27 PM

val a = 5 
val b = 5.4
val c = 5.4321

08/21/2018, 3:29 PM

yes, it is infered when possible

Steven McLaughlin

08/21/2018, 3:40 PM

You can see for yourself with something like this

println(a.javaClass.kotlin)
    println(b.javaClass.kotlin)
    println(c.javaClass.kotlin)

karelpeeters

08/21/2018, 3:52 PM

Might as well go for

a.javaClass.kotlin.java.kotlin

08/21/2018, 4:14 PM

Those determine the runtime type, not the static type of the variable at compile time.

Steven McLaughlin

08/21/2018, 5:03 PM

Ah, I think I misunderstood what he was asking

08/21/2018, 5:18 PM

@diesieben07 what's the difference between runtime type and static type?

08/21/2018, 5:19 PM

val a: Any = 1

has runtime type

Int

but static type

Any

08/21/2018, 5:19 PM

So which mean if I define

val a = 1

In runtime it shows

Int

but in static it is

Any

08/21/2018, 5:21 PM

No, in that case the compiler will infer the type

Int

, so both static and runtime type will be

Int

. But take this more complicated example:

fun iReturnAny(): Any = 3
val a = iReturnAny()

Compiler will infer

Any

iReturnAny()

Any

), but runtime type will

Int

08/21/2018, 5:22 PM

This is clear.

The static type will assign based on the return type of the function.

However, the runtime type will infer as Int.

08/21/2018, 5:24 PM

No. Runtime type is not inferred. Runtime type is the type of the value actually being there at runtime. You can put anything into a variable of type

Any

. The static type will always be

Any

, but the runtime type could be

String

(if there is a string in there) or anything else.

Type inference happens at compile time and it only determines the static (compile time) type of something.

08/21/2018, 5:26 PM

Does it matter if the type infer on runtime or static?

08/21/2018, 5:27 PM

Again: type inference only happens at compile time.

You can think of type inference as the compiler "typing the obvious for you"

val a = 3

- What type does

have? Well, it's an

Int

, "obviously", so let's "type that for you":

val a: Int = 3

That is type inference (basically)

karelpeeters

08/21/2018, 5:30 PM

You can always check with

Ctrl + Q

on the variable.

08/21/2018, 5:31 PM

That's a great tip!