Java Enhanced For Loop - 编辑原始数组值 [英] Java Enhanced For Loop - Editing Original Array Values

问题描述

我想详细了解Enhanced For循环如何在Java中工作（假设我知道这个循环的基本用法，以及它如何工作）。

给出以下代码：

$ p $ String [] a = { 狗，猫，乌龟};

（String s：a）{
out.println（String：+ s）;
s = in.readLine（New String？）;
}


它实际上并不修改原始列表a。
为什么不呢？内存管理如何工作？是不是对a [i]的同一个存储单元的引用？

我在oracle文档上看到，增强for循环不能用于从原始数组中删除元素，这是有道理的。修改值是否相同？

提前致谢

解决方案

是不是引用了'a [i]'的同一个内存单元？

原来是的。但是， in.readLine 会生成一个新的String对象的引用，然后用它来覆盖 s 。但是只有 s 被覆盖，而不是基础字符串，也不是数组中的引用。

I'd like to know, in detail, how the Enhanced For Loop works in Java (assuming i do get how the basic usage of this loop is and how it works in general).

Given the following code:

String[] a = {"dog", "cat", "turtle"};

for (String s : a) {
  out.println("String: " + s);
  s = in.readLine("New String? ");
}

It doesn't actually modify the original list 'a'. Why not? How memory Management works? Isn't 's' a reference to the same memory cell of 'a[i]'?

I read on the oracle documentation that enhanced for loops can't be used to remove elements from the original array, it makes sense. Is it the same for modifying values?

Thanks in advance

解决方案

Isn't 's' a reference to the same memory cell of 'a[i]'?

Originally, yes. But then in.readLine produces a reference to a new String object, which you then use to overwrite s. But only s is overwritten, not the underlying string, nor the reference in the array.

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