Iterate through array in Kotlin to replace elements

I’m learning Kotlin and I want to iterate through array to replace some elements.

To change something inside elements I do this:

if (arr != null){         // Kotlin doesn't like NullReferenceException
    for(elem in arr) {    // for each element
        elem.property++;  // do something with element
    }
}

But when I want to replace element at some position I have to do this:

if (arr != null){                           // Kotlin doesn't like NullReferenceException
    if (arr.size > 0) {                     // check size
        for (i in 0..arr.size - 1) {        // for all elements
            if (i == 5){                    // if something
                arr[i] = buildNewElement(); // replace element
            }
        }
    }
}

This is a bit ugly.

Does Kotlin offer something nicer or something that could reduce lines of code?

>Solution :

So first of all, because you are using kotlin you should rarely need to do a if (someVal != null) check. Nullable types have a safe call operator that you can use instead: ?.

If the requirement is to keep the array in place, consider using forEachIndexed (with the usual caveats about modifying an array in-place):

arr?.forEachIndexed { i, value ->
    arr[i] = buildNewElement()
}

If you don’t need to use value, you can rename it to _

If you do not need to do this in-place and can generate a new array, you should instead consider map