One issue I could see with this is the "magic numbers". I think for best readability later it would be good to give everything an explicit variable name.

Nice solution

Wow !
All ingenious is simple.

do you mean this is very good way to do this task ?

how about the below string,
val str: String = "a!b#dfe-;;"

i think you need to filter letter only
:)

I more like when expression

Then fix the tests

first draft, no refactor, yes it's ugly :D

This is probably the fastest solution, but requires Java 8 (which might be a problem e.g. on Android). One minor note: Math.abs is redundant here. ;)

nothing to do anymore about that, so, resolving...

fixed

fixed. But you'll have to change the name of the method to findSmallestInt.