如果字符串的长度为2并且包含1个字母和1个数字，则正则表达式匹配

Question

Guys I hate Regex and I suck at writing.

I have a string that is space separated and contains several codes that I need to pull out. Each code is marked by beginning with a capital letter and ending with a number. The code is only two digits.

I'm trying to create an array of strings from the initial string and I can't get the regular expression right.

Here is what I have

String[] test = Regex.Split(originalText, "([a-zA-Z0-9]{2})");

I also tried:

String[] test = Regex.Split(originalText, "([A-Z]{1}[0-9]{1})");

I don't have any experience with Regex as I try to avoid writing them whenever possible.

Anyone have any suggestions?

Example input:

AA2410 F7 A4 Y7 B7 A 0715 0836 E0.M80

I need to pull out F7, A4, B7. E0 should be ignored.

Answer 1

You want to collect the results, not split on them, right?

Regex regexObj = new Regex(@"\b[A-Z][0-9]\b");
allMatchResults = regexObj.Matches(subjectString);

should do this. The \\b s are word boundaries, making sure that only entire strings (like A1 ) are extracted, not substrings (like the A1 in TWA101 ).

If you also need to exclude "words" with non-word characters in them (like E0.M80 in your comment), you need to define your own word boundary, for example:

Regex regexObj = new Regex(@"(?<=^|\s)[A-Z][0-9](?=\s|$)");

Now A1 only matches when surrounded by whitespace (or start/end-of-string positions).

Explanation:

(?<=  # Assert that we can match the following before the current position:
 ^    # Start of string
|     # or
 \s   # whitespace.
) 
[A-Z] # Match an uppercase ASCII letter
[0-9] # Match an ASCII digit
(?=   # Assert that we can match the following after the current position:
 \s   # Whitespace
|     # or
 $    # end of string.
)

If you also need to find non-ASCII letters/digits, you can use

\p{Lu}\p{N}

instead of [AZ][0-9] . This finds all uppercase Unicode letters and Unicode digits (like Ä٣ ), but I guess that's not really what you're after, is it?

Answer 2

Do you mean that each code looks like "A00"?

Then this is the regex:

"[AZ][0-9][0-9]"

Very simple... By the way, there's no point writing {1} in a regex. [0-9]{1} means "match exactly one digit, which is exactly like writing [0-9] .

Don't give up, simple regexes make perfect sense.

Answer 3

This should be ok:

String[] all_codes = Regex.Split(originalText, @"\b[A-Z]\d\b");

It gives you an array with all code starting with a capital letter followed by a digit, separated by an kind of word boundary (site space etc.)