正则表达式 （或）在其中

Question

I have a long RegEx that is working, but I have a section at the end that is perplexing me. I have a scenario where I am parsing some HTML and one of two scenarios can happen. Either the pattern I am searching for ends with a X followed immediately by a single digit or it's a   . Here's the RegEx fragment:

(X(\d+)| )

As you might have noticed, I don't care about the X or the   , I just want to capture the digit if it's there. It appears that in order to use the |, I have to use a capture group. So now I get BOTH X5 AND 5 if that pattern exists. I really just want the digit captured if it's there.

Thanks!

Answer 1

To get the effect of grouping, without the effect of capturing, use the (?:...) notation:

(?:X(\d+)| )

This is equivalent to what you wrote, except that it doesn't create a capture group for X5 , only for 5 .

(By the way, you say "a single digit", but your regex has \\d+ rather than \\d , so it can actually match multiple digits.)

Answer 2

您可以使用非捕获组吗？

(?:X(\d+)| )

Answer 3

try

(?:X(\d+)| )

adding ?: you actually disable the backreference while grouping.

Answer 4

使用非捕获组：

(?:X(\d+)| )