I am trying to extract an alphanumeric sequence from text. This sequence could be either five or six characters in length, must start and end with a number, and have at least one letter in between, for example: 25D212, 4WX07, 8FZW5, 2T784, 25XR47
This is what I was able to put together
[0-9][[0-9]|[a-zA-Z]]{3,4}[0-9]
The issue with this solution is that it also matches
888888 (at least one character constraint not being met)
generalized
Based on the permutations (below), it looks like it can be generalized to this
# (?i)\d(?=\d{0,3}[a-z])[a-z\d]{3,4}\d
(?i)
\d # A digit
(?= \d{0,3} [a-z] ) # a letter in the next 1 to 4 characters
[a-z\d]{3,4} # 3 to 4 digits or letters
\d # A digit
permutations
# (?i)\d(?:[a-z][a-z\d]{2,3}|\d[a-z][a-z\d]{1,2}|\d\d[a-z][a-z\d]{0,1}|\d\d\d[a-z])\d
(?i)
\d
(?:
[a-z]
[a-z\d]{2,3}
|
\d
[a-z]
[a-z\d]{1,2}
|
\d\d
[a-z]
[a-z\d]{0,1}
|
\d\d\d
[a-z]
)
\d
Input
for example: 25D212, 4WX07, 8FZW5, 2T784, 25XR47
Output
** Grp 0 - ( pos 13 , len 6 )
25D212
** Grp 0 - ( pos 21 , len 5 )
4WX07
** Grp 0 - ( pos 28 , len 5 )
8FZW5
** Grp 0 - ( pos 28 , len 5 )
8FZW5
** Grp 0 - ( pos 42 , len 6 )
25XR47
You may be able solve this with one regex pattern, but you can definately solve it with two patterns.
First pattern will be something like:
\d[0-9a-zA-Z]{3,4}\d
(Note: \d is the same as [0-9])
Second pattern will be this:
\d+[a-zA-Z]+\d+
The first pattern controls the size of the string, the second confirms that it contains at least one alpha character.
Good resource for testing Java regex patterns: http://www.regexplanet.com/advanced/java/index.html
Looks like the Avinash Raj post is the correct answer. I'm leaving mine as an option (suboptimal as it may be)
@Avinash Raj already has a good-looking pattern, but I wanted to share my alternative:
\b(?=[0-9a-zA-Z]{5,6}\b)\d.*[a-zA-Z].*\d\b
This may be easier for you to read if you split it apart into the look-ahead assertion that tests for a 5-6 character string of alphanumerics, and the actual pattern that tests the format (of starting and ending with a digit and having a letter somewhere in the middle). This roughly corresponds to how you phrased the question initially, so it may be easier to read and remember going forward "what the heck does this do?"
