Extract an ISBN with regex

Question

I have an extremely long string that I want to parse for a numeric value that occurs after the substring \"ISBN\". However, this grouping of 13 digits can be arranged differ

Answer 1

• Alternative 1:

  pattern.matcher(ISBN.replace("-", ""))
  

• Alternative 2: Something like

  Pattern.compile("(\\d-?){13}")
  

Demo of second alternative:

String ISBN = "ISBN: 123-456-789-112-3, ISBN: 1234567891123";

Pattern pattern = Pattern.compile("(\\d-?){13}");
Matcher matcher = pattern.matcher(ISBN);

while (matcher.find())
    System.out.println(matcher.group());

Output:

123-456-789-112-3
1234567891123