ArrayList.size() 方法是否被缓存?

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问题描述

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我想知道，您可以在现有 ArrayList 上调用的 size() 方法是否已缓存?或者在性能关键代码中我只是将 size() 存储在本地 int 中更可取?

I was wondering, is the size() method that you can call on a existing ArrayList<T> cached? Or is it preferable in performance critical code that I just store the size() in a local int?

我希望它确实被缓存，当您不在对 size() 的调用之间添加/删除项目时.

I would expect that it is indeed cached, when you don't add/remove items between calls to size().

我说得对吗?

更新
我不是在谈论内联或诸如此类的事情.我只想知道方法 size() 本身是在内部缓存该值，还是每次调用时动态计算.

update
I am not talking about inlining or such things. I just want to know if the method size() itself caches the value internally, or that it dynamically computes every time when called.

推荐答案

我不认为我会说它是缓存"的——但它只是存储在一个字段中，所以它足够快，可以经常调用.

I don't think I'd say it's "cached" as such - but it's just stored in a field, so it's fast enough to call frequently.

size() 的 Sun JDK 实现只是:

The Sun JDK implementation of size() is just:

public int size() {
    return size;
}

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