什么是呼叫array.length的成本

在更新for循环为，在每一个我们的应用程序循环，我碰到很多这样的模式来了：

While updating for loops to for-each loops in our application, I came across a lot of these "patterns":

for (int i = 0, n = a.length; i < n; i++) {
    ...
}

而不是

for (int i = 0; i < a.length; i++) {
    ...
}

我可以看到你获得对收藏的性能，因为你不需要调用的尺寸（）的方法，每个循环。但随着阵列??

I can see that you gain performance for collections because you don't need to call the size() method with each loop. But with arrays??

于是问题出现了：是 array.length 比普通的可变更为昂贵

So the question arose: is array.length more expensive than a regular variable?