codewars #31 extract file name (6kyu)

 #31 extract file name

ou have to extract a portion of the file name as follows:

Assume it will start with date represented as long number

Followed by an underscore

Youll have then a filename with an extension

it will always have an extra extension at the end

Inputs:

1231231223123131_FILE_NAME.EXTENSION.OTHEREXTENSION

1_This_is_an_otherExample.mpg.OTHEREXTENSIONadasdassdassds34

1231231223123131_myFile.tar.gz2

Outputs

FILE_NAME.EXTENSION

This_is_an_otherExample.mpg

myFile.tar

The recommend way to solve it is using RegEx and specifically groups.

public class FileNameExtractor {
    public static String extractFileName(String s) {
       return s.replaceAll("^\\d+\\_|\\.[^.]+$", "");
    }
}