正则表达式：索引附近的未封闭字符类

Question

I am not very familiar with Regex and I have some issue with a regex string in Java. I get the following error:

Unclosed character class near index 198

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"(?=^[\\x00-\\x7F]+$)^(([^<>()|[\\]\\\\.,;:\\s@\\\"\"]+(\\.[^<>()[\\]\\\\.,;:\\s@\\\"\"]+)*)|(\\\"\".+\\\"\"))@((\\[(2([0-4]\\d|5[0-5])|1?\\d{1,2})(\\.(2([0-4]\\d|5[0-5])|1?\\d{1,2})){3} \\])|(([a-zA-Z\\-0-9]+\\.)+[a-zA-Z]{2,}))$"

Could anyone enlighten me on this issue?

Original received pattern from web team is this (and it's a valid regex if we check it here ):

(?=^[\x00-\x7F]+$)^(([^<>()|[\]\\.,;:\s@\""]+(\.[^<>()[\]\\.,;:\s@\""]+)*)|(\"".+\""))@((\[(2([0-4]\d|5[0-5])|1?\d{1,2})(\.(2([0-4]\d|5[0-5])|1?\d{1,2})){3} \])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$

Thanks

Answer 1

There are multiple shortcomings in the pattern, but the severest issue is that in Java regex, you need to escape [ inside a character class.

You also can use the anchored look-ahead after ^ (no need to use two ^ in the pattern then).

Also, no need to use [\\""] , as ["] will already match a single " .

String rx = "^(?=[\\x00-\\x7F]+$)(([^<>()|\\[\\]\\\\.,;:\\s@\"]+(\\.[^<>()\\[\\]\\\\.,;:\\s@\"]+)*)|(\\\"\".+\\\"\"))@((\\[(2([0-4]\\d|5[0-5])|1?\\d{1,2})(\\.(2([0-4]\\d|5[0-5])|1?\\d{1,2})){3} \\])|(([a-zA-Z0-9-]+\\.)+[a-zA-Z]{2,}))$";

Please also check \\\\\\"\\".+\\\\\\"\\" , not sure you need to match ""something here"" .

See IDEONE demo