Java - 在正则表达式中转义元字符 [ 和 ]
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Java - Escaping Meta-characters [ and ] in Regex
提问by ZirconCode
I am attempting to replace the first occurrence of the string "[]" in another string:
我试图替换另一个字符串中第一次出现的字符串“[]”：
aString.replaceFirst("[]", "blah");
aString.replaceFirst("[]", "等等");
I get the error: java.util.regex.PatternSyntaxException: Unclosed character class near index 1 []
我收到错误消息：java.util.regex.PatternSyntaxException：索引 1 附近未关闭的字符类 []
[ and ] are obviously metacharacters, however when I try to escape them with a \ eclipse complains that it is not a valid escape sequence.
[ 和 ] 显然是元字符，但是当我尝试用 \ eclipse 转义它们时，它会抱怨它不是有效的转义序列。
I've looked but couldn't find, what am I missing?
我找过但找不到，我错过了什么？
Thank You
谢谢
回答by user268396
Regex patterns use \as escape character, but so does Java. So to get a singleescape (\) in a regex pattern you should write: \\. To escape an escape inside a regex, double the pattern: \\\\.
正则表达式模式\用作转义字符，但 Java 也是如此。因此，要在正则表达式模式中获得单个转义符 ( \)，您应该这样写：\\. 要在正则表达式中转义，请将模式加倍：\\\\.
Of course that's extremely tedious, made all the worse because regexes have a ton of escape sequences like that. Which is why Java regexes also support “quoting” litteral parts of the pattern and this allows you to write your pattern as: \\Q[]\\E.
当然，这非常乏味，而且更糟，因为正则表达式有大量这样的转义序列。这就是为什么 Java 正则表达式还支持“引用”模式的文字部分，这允许您将模式编写为：\\Q[]\\E.
EDIT: As the other answer hints at: java.util.regex.Pattern.quote()performs this wrapping between \\Qand \\E.
编辑：正如另一个答案所暗示的：java.util.regex.Pattern.quote()在\\Q和之间执行这种包装\\E。
回答by pushy
Try \\[ and \\]. You need to double escape, because \ is also an escape character for strings (as is \" when you want to have double-quotes in your text). Therefore to get a \ in your string you have to use \\.
试试 \\[ 和 \\]。您需要双重转义，因为 \ 也是字符串的转义字符（当您想在文本中使用双引号时，就像 \" 一样）。因此，要在字符串中获得 \，您必须使用 \\。
回答by ratchet freak
aString.replaceFirst("\[\]", "blah");
or in the more general case
或者在更一般的情况下
aString.replaceFirst(java.util.regex.Pattern.quote("[]"), "blah");
