检查变量null之前分配null？ [英] Check if variable null before assign to null?

问题描述

与空检查相比，变量赋值是否昂贵？例如，是否值得检查foo不为空，然后再赋值为null？

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;
}

或者这是什么都不担心？

Or is this worrying about nothing?

推荐答案

这是一个微微优化（可能由编译器处理的东西）。不要担心。

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.

我们应该忘记小的效率，说大约97％的时间：过早优化是一切邪恶的根源。 - Donald Knuth

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

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