Regex to match N number of digits ignoring break lines only

Question

I need to build a regex in Java that matches N number of digits ignoring Line Breaks. Please see the example below:

Here is string

1234567
891011234

I found a solution asking to do this way:

(\d\D*){16}

It doesn't work because it would match this>

1234567smth
891011234

Or even match if I have a White Space instead of "smth", and I don't want this..

Please notice that the line break can be in any part of the sequence of digits

So the expression should match this also:

123
4567891011234

Thank you

Answer 1

Try this, which match 16 digits, but allows any number of newlines within the number:

str.matches("(\\d\\R*){16}")

fyi, \R means "any Unicode linebreak sequence"

To allow at most 1 newline within the digits, change * to ? .

---

"1234567\n891011234".matches("(\\d\\R*){16}") // true

"1234567\n8910112349999".matches("(\\d\\R*){16}") // false
"1234567\n891011234foo".matches("(\\d\\R*){16}") // false
"1234567\n89101123".matches("(\\d\\R*){16}") // false