What is the most clean way to rewrite this in kotlin

if ( a == null ) {
do something 
} else {
do something else
}

That's pretty clean as it is. Unless there's more details about "do something".

I use a?.let { do something } but don't know how to handle when a is null

In my opinion, for your use case I suggest keeping it simple with if/else. Or you'll end up with awkward chains of

?:

and

?.

.

I agree, I was just pointing out to OP how to handle the "else" case

@Dominaezzz But that isn't very kotlin-y right?

May be the "do something" should be in the A object. like

a?.doSomething()

(edit: whops, works only if you don't have 2 branches)

@Abdul Kadir Depends on the use case.

@stephan_marshay that doesn't necessarily handle the "else" case though? If whatever is in the let expression returns

null

then it will also execute whatever after

?:

was You would have to use

also

or

apply

then Personally I might go for a

when (a) {
  null -> doSomething()
  else -> doSomethingElse()
}

https://arrow-kt.io/docs/arrow/core/option/ (disclaimer I haven't used kotlin much but IMO options are the cleanest way of handling nullality)