Java foreach 对原语的迭代顺序是否精确定义?

2022-01-24 00:00:00 iteration foreach java

示例代码:

int a[] = new int[]{0, 1, 2, 3};
int result = 0;
for (int i : a)
    result += i;

是否保证循环遍历 a[0], a[1], a[2], a[3] 按那个顺序?我坚信答案是肯定的，但是 这个页面 似乎没有明确说明顺序.

Is the loop guaranteed to iterate across a[0], a[1], a[2], a[3] in that order? I strongly believe the answer is yes, but this page seems to not unambiguously state order.

有可靠的参考吗?

推荐答案

根据JLS，增强的for语句，你的for循环相当于

According to the JLS, The enhanced for statement, your for-loop is equivalent to

int[] array = a;
for (int index = 0; index < a.length; index++) {
    int i = array[index];
    result += i;
}

"其中 array 和 index 是编译器生成的标识符，它们不同于在范围内的任何其他标识符(编译器生成的或其他标识符)出现增强的 for 语句."(这里稍微解释一下变量名).

"where array and index are compiler-generated identifiers that are distinct from any other identifiers (compiler-generated or otherwise) that are in scope at the point where the enhanced for statement occurs." (slightly paraphrasing the variable names here).

所以是的:订单绝对有保证.

So yes: the order is absolutely guaranteed.

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