How to idiomatically test for non-null, non-empty strings in Kotlin?

You can use isNullOrEmpty or its friend isNullOrBlank like so:

if(!s.isNullOrEmpty()){
    // s is not empty
}

Both isNullOrEmpty and isNullOrBlank are extension methods on CharSequence? thus you can use them safely with null. Alternatively turn null into false like so:

if(s?.isNotEmpty() ?: false){
    // s is not empty
}

you can also do the following

if(s?.isNotEmpty() == true){ 
    // s is not empty
}