Does anyone know this or do I have to check using ...

# announcements

[hallvard]

Does anyone know this or do I have to check using javap: if I re-set the value of a String thus: author = someNullableFunction() ?: author, will the compiler be smart enough to turn the statement into a null check, thus avoiding re-setting a value that is not really changing in situations where the function returns null?

[diesieben07]

I doubt it, because thats not what you are telling it to do.

[diesieben07]

Imho you should just use an if-statement instead of trying to write "clever" code

[tseisel]

It will do something like the following:

val nullableFunctionResult = someNullableFunction()
if (nullableFunctionResult != null) {
    author = nullableFunctionResult
} else {
    author = author
}

But bytecode optimizers like Proguard/R8, or even the JVM runtime should easily optimize such scenario.

[hallvard]

Am I not telling the code to do so? That's debatable. Are there cases where there's a difference?

[diesieben07]

If author has a custom setter (or even is just a field, maybe volatile) then yes, there is a difference

[hallvard]

If my author = author case is not optimized away, I will indeed go with Thibault's suggestion, except for the else part, which is the part I want to avoid anyway. Thanks.

[hallvard]

Custom setter, good point.

[hallvard]

Even though the compiler could check that too ...