英文:
Counting Operations of String Concatenation in Java
问题
我正在尝试理解为什么在Java中，字符串拼接的时间复杂度是O(n)。
我们被告知 s1 + s2 不仅会创建一个新的字符串，其长度为 s1.length() + s2.length()，还会将 s1 和 s2 复制到这个新字符串中。
因此，他们计算出了以下成本：2 + 2(n+1) + 1 => (5 + 2n)。
我不确定我是否理解我的讲师是如何得出这个计算结果的。是否有人介意向我解释一下字符串拼接的操作，以证明上述提到的成本呢？
英文:
I'm trying to understand why String Concatenation is O(n) time complexity in Java.
We were told that s1 + s2 is going to both create a new string with length of s1.length() + s2.length(), and copy s1 and s2 into that new string.
So the following cost was calculated (by them) 2 + 2(n+1) + 1 => (5 + 2n)
I'm not sure I understand how my lecturers got that calculated. Would anyone mind explaining the operations of string concatenation to me that justifies the above mentioned cost?
答案1
得分: 0
以下是翻译好的内容：
我会谨慎地对 Java 中的字符串拼接进行假设，因为从 Java 9 开始，其内部发生了变化。
关于这个主题的一个很好的演示可以在这里找到：https://www.javaspecialists.eu/talks/pdfs/2018%20Voxxed%20in%20Thessaloniki,%20Greece%20-%20%22Enough%20java.lang.String%20to%20Hang%20Ourselves%20...%22%20by%20Heinz%20Kabutz.pdf
另外值得阅读的资源：https://dzone.com/articles/jdk-9jep-280-string-concatenations-will-never-be-t
虽然有点老了，但对你可能仍有参考价值：https://stackoverflow.com/a/15401136/875083
英文:
I would be careful making assumptions regarding what is happening during String concatenation in Java since it changed internally starting with Java 9.
A good presentation regarding this topic can be found here: https://www.javaspecialists.eu/talks/pdfs/2018%20Voxxed%20in%20Thessaloniki,%20Greece%20-%20%22Enough%20java.lang.String%20to%20Hang%20Ourselves%20...%22%20by%20Heinz%20Kabutz.pdf
Also worth reading: https://dzone.com/articles/jdk-9jep-280-string-concatenations-will-never-be-t
And already a bit older but maybe relevant to you: https://stackoverflow.com/a/15401136/875083
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