Java中的过早优化：何时使用“x = foo.getX（）” vs简单地说“foo.getX（）” [英] Premature optimization in Java: when to use "x = foo.getX()" vs simply "foo.getX()"

问题描述

当我发现自己多次调用相同的getter方法时，这应该被视为一个问题吗？ [总是]分配给局部变量并且只调用一次会更好吗？

When I find myself calling the same getter method multiple times, should this be considered a problem? Is it better to [always] assign to a local variable and call only once?

我确定答案当然是它取决于。

I'm sure the answer of course is "it depends".

我更关心的是更简单的情况，即getter只是一个传递私有变量值类型的方法。即没有涉及昂贵的计算，没有消耗数据库连接等等。

I'm more concerned about the simpler case where the getter is simply a "pass-along-the-value-of-a-private-variable" type method. i.e. there's no expensive computation involved, no database connections being consumed, etc.

我的它是否更好的问题涉及代码可读性（样式）和性能。即具有如此大的性能影响：

My question of "is it better" pertains to both code readability (style) and also performance. i.e. is it that much of a performance hit to have:

SomeMethod1(a, b, foo.getX(), c);
SomeMethod2(b, foo.getX(), c);
SomeMethod3(foo.getX());

vs：

X x = foo.getX();
SomeMethod1(a, b, x, c);
SomeMethod2(b, x, c);
SomeMethod3(x);

我意识到这个问题有点挑剔和灰色。但我刚才意识到，我根本没有一致的方法来评估这些权衡。钓鱼的标准不仅仅是完全异想天开。

I realize this question is a bit nit-picky and gray. But I just realized, I have no consistent way of evaluating these trade-offs, at all. Am fishing for some criteria that are more than just completely whimsical.

谢谢。

推荐答案

选择不应该是关于性能损失而是关于代码可读性。

The choice shouldn't really be about performance hit but about code readability.

当你创建一个变量时，你可以给它一个它应得的名字。目前的背景。当你多次使用相同的值时，它肯定具有真正的意义，而不仅仅是方法名称（或者更糟糕的方法链）。

这真的更好看：

When you create a variable you can give it the name it deserves in the current context. When you use a same value more than one time it has surely a real meaning, more than a method name (or worse a chain of methods).
And it's really better to read:

String username = user.getName();
SomeMethod1(a, b, username, c);
SomeMethod2(b, username, c);
SomeMethod3(username);

比

SomeMethod1(a, b, user.getName(), c);
SomeMethod2(b, user.getName(), c);
SomeMethod3(user.getName());

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