Regular Expression - Start with 3538 and then contain 8 digits

E.g. match 353812345678 So far I have ^3538{1}[\d]{8} which开发者_如何学JAVA works but does not restrict the length. How do I make sure the length is only a maximum of 12 digits?

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If you want the number to be the only thing in the string: ^3538\d{8}$

If you just want the number in a string: \b3538\d{8}\b

^ is the start-of-string anchor, while $ is the end-of-string anchor, so the first one restricts the number to be the only thing on the line.

In the other one, \b means a word boundary, so it just means no other letters or digits may come directly before or after the number.

Also, note, in your original regex, the {1} is redundant, and [\d] means the same as \d.

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^3538{1}[\d]{8}[^\d] will ensure you have 3538 followed by 8 digits and something that is NOT a digit -- thus limiting the length.

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Add a dollar sign ($) at the end of the regex: ^3538{1}[\d]{8}$