Check if variable null before assign to null?

Question

Is variable assignment expensive compared to a null check? For example, is it worth checking that foo is not null before assigning it null?

if (foo != null) {
     foo = null;
}

Or is this worrying about nothing?

Answer 1

This is a micro-micro-optimization (and possibly something handled by the compiler anyways). Don't worry about it. You'll get a far greater return by focusing on your programs actual algorithm.

We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. -- Donald Knuth