字符串替换方法不替换字符 [英] String replace method is not replacing characters

问题描述

我有一个作为字符串传入的句子，我正在替换单词and"，我想用"替换它.它并没有用空格代替and"这个词.下面是我的逻辑示例.当我调试它时，逻辑确实属于句子.替换.

I have a sentence that is passed in as a string and I am doing a replace on the word "and" and I want to replace it with " ". And it's not replacing the word "and" with white space. Below is an example of my logic. And when I debug this the logic does fall into the sentence.replace.

String sentence = "Define, Measure, Analyze, Design and Verify"
if (sentence.contains("and")){
    sentence.replace("and", " ");
}

我在这里遗漏了什么.

推荐答案

当我调试这个时，逻辑确实落入了sentence.replace.

And when I debug this the logic does fall into the sentence.replace.

是的，然后您丢弃返回值.

Yes, and then you discard the return value.

Java 中的字符串是不可变的——当你调用 replace 时，它不会改变 现有 字符串的内容——它返回一个 new 修改后的字符串.所以你想要:

Strings in Java are immutable - when you call replace, it doesn't change the contents of the existing string - it returns a new string with the modifications. So you want:

sentence = sentence.replace("and", " ");

这适用于所有 String 中的方法(substring、toLowerCase 等).没有改变字符串的内容.

This applies to all the methods in String (substring, toLowerCase etc). None of them change the contents of the string.

请注意，您实际上并不需要在条件中执行此操作 - 毕竟，如果句子 doesn't 包含 "and"，则没有任何危害执行替换:

Note that you don't really need to do this in a condition - after all, if the sentence doesn't contain "and", it does no harm to perform the replacement:

String sentence = "Define, Measure, Analyze, Design and Verify";
sentence = sentence.replace("and", " ");

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