使用点时 String.split 返回 null [英] String.split returning null when using a dot

问题描述

我得到了这个简单的代码:

I got this simple code:

String ip = "1.2.3.4";
String[] ipArray = ip.split(".");
System.out.println(ipArray[1]);

并且 ipArray 在它遇到 System.out.println 时为空(抛出空指针异常).

And ipArray is null by the time it hits System.out.println (throws null pointer exception).

我的问题是为什么即使我将 ipArray 设置为在每个 ip 的 .s 上拆分，为什么 ipArray 仍为空?

My question is why does ipArray stay null even though I'm setting it to split on each of ip's .s?

推荐答案

使用ip.split("\\.");，你的问题就会迎刃而解.问题是 String#split 接收正则表达式，点 (.) 符号是正则表达式中的特殊字符，因此您需要对其进行转义才能将其解释为普通点，反斜杠也是转义Java中的字符，你也必须转义它.

Use ip.split("\\."); and your problems will be solved. The problem is that String#split receives a regular expression, the dot (.) symbol is a special character in regular expressions, so you need to escape it for it to be interpreted as a plain dot, also as the backslash is an escape character in Java, you have to escape it too.

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