Regex to capture 2 consecutive digits, but don't capture if 3 or more

Question

For example. If I have 1234X03.04

I want to capture the 03 and 04 But I don't want 12, 23, 34

I understand:

• negative lookahead: (?!...)
• negative lookbehind: (?<!...)

But, I don't know how to combine that into a single regex. Can someone help me out? Cheers.

Answer 1

You can use:

(?<!\d)\d{2}(?!\d)

• (?<!\d) - prior char is not a digit
• \d{2} - exactly two consecutive digits
• (?!\d) - next char is not a digit

Here's a demo of the results in PHP. I think PHP's regex is close to Java's.