java - (String) or .toString()?

Question

I have a method with an Object o parameter.

In this method, I exactly know there is a String in "o" which is not null. There is no need to check, or do something else. I have to treat it exactly like a String object.

Just curious - what is cheaper - cast it to String, or use Object.toString()? Or is it same by time-/cpu-/mem- price?

Update: The method accepts Object because it's the implementation of an interface. There is no way to change the parameter type.

And it can't be null at all. I just wanted to say that I do not need to check it for null or emptyness. In my case, there is always a nonempty string.

Answer 1

casting to a String is cheaper since that doesn't require an external function call, just internal type checking.