One line RegEx to match 6 alphanumeric with exactly 2 alphabetic

Question

I am trying to figure out how to use positive lookahead to get this to work with no success. I am playing with something similar to:

^(?=.*[a-zA-Z0-9])(\w{6})$

The only requirements are that
1. the string is 6 characters
2. has exactly 2 alphabetic and 4 digits.

So positive matches would be:

A0123A
AA0123
0123AA
A01A23

Answer 1

Your ^(?=.*[a-zA-Z0-9])(\\w6)$ matches a string that has at least 1 ASCII letter or digit (due to (?=.*[a-zA-Z0-9]) ) and only has 1 word character followed with a 6 symbol. So, it will match strings like 16 or _6 , or a6 . Thus, it will not work as you expect.

You may use

^(?=.{6}$)\d*(?:\p{L}\d*){2}$

See the regex demo

Explanation :

• ^ - start of string
• (?=.{6}$) - a check that makes sure there are 6 characters in the string
• \\d* - zero or more digits
• (?:\\p{L}\\d*){2} - 2 sequences of a letter and 0+ digits
• $ - end of string

If you need to limit the expression to matching ASCII letters and digits, replace \\p{L} with [a-zA-Z] and \\d with [0-9] .

Also, to make sure you match at the start and the very end of the string, use \\z anchor instead of $ .