Question

I would like to know how to parse the last 6 digits from a Java string. So:

String input1 = "b400" // the regex should return b400  
String input2 = "101010" // the regex should return 101010  
String input3 = "12345678" // the regex should return 345678  

Answer 1

No regex needed.

input.substring(Math.max(0, input.length() - 6));

If it has to be a regex for API reasons,

Pattern.compile(".{0,6}\\Z", Pattern.DOTALL)

If you need to match the last 6 codepoints (incl. supplementary codepoints), then you can replace . with (?:[\\ud800-\\udbff][\\udc00-\\udfff]|.){0,6}