在Java中的ArrayList中的元素修改时foreach循环不工作

问题描述：

检查了这一点：

import java.util.ArrayList;
public class passbyReferenceOrValue {

    public static void main(String[] args) {
        ArrayList<String> c=new ArrayList<>();
        c.add("abc");
        for (String k : c) {
            k+="l";
        }
        System.out.println(c);

    }
}

结果是[ABC]，为什么呢？
好吧，为了发布这个问题我不得不添加更多的细节，那就是这是一个测试code我写的，因为我遇到了使用for-each循环的另一个问题，当我这样做，我真的饿了，需要一个伟大的晚餐，顺便说一句，我认为这是不够的详细信息

result is [abc], why? Well, in order to post this question I have to add more detail, that is this is a testing code I wrote because i met another problems using for-each loop, and when I was doing that, I`m hungry and need a great dinner, by the way, I think it is enough for the "details"

答

在您从 ArrayList中获得字符串值每次循环迭代键，将其存储在 K 的参考，像

In each loop iteration you are getting String value from ArrayList and storing it in k reference, something like

for (int i = 0; i < c.size(); i++) {
    String k = c.get(i);//now k is reference to object from list
}

接下来，在 K + =L; 你正在做的是执行 K = K +L这将创造新的字符串，并将其放在 K 引用

Next in k+="l"; all you are doing is executing k = k + "l" which will create new string and place it in k reference

    String k = c.get(i);//now k is reference to object from list
    k = k + "l"; //now k holds new object

所以这并不影响的ArrayList 。

如果你想改变抗衡ArrayList的，那么你不应该通过每个循环，但通过正常的循环像

If you want to change contend of ArrayList then you shouldn't be doing it via for each loop but via normal for loop like

for (int i = 0; i < c.size(); i++) {
    c.set(i, c.get(i)+"l");
}

在Java中的ArrayList中的元素修改时foreach循环不工作

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