Question

I am trying to match a string containing 1 to 3 digits,

example:

1
 2
123
  3

This is what i tried,

[\s]?[0-9]{1,3}[\s]?

This is matching,

123 ->a space after 123

Answer 1

Your question is unclear, but it seems you’re looking for a string that

• is exactly 3 characters long
• contains only digits or whitespace
• contains at least one digit

In that case, the regex is ^(?=.*\d)[\d\s]{3}$. As a Java string: "^(?=.*\\d)[\\d\\s]{3}$".

Explanation:

^         # Start of string
(?=.*\d)  # Assert that there is at least one digit in the string
[\d\s]{3} # Match 3 digits or whitespace characters
$         # End of string