I've found a good reference that helps to understand regular expression with GREP.
Have a look at this site http://www.robelle.com/smugbook/regexpr.html
Yann
Pattern pattern = Pattern.compile("^([a-zA-Z0-9]*)_(\\d*)?_?(.*)-\\d*_.*$"); Matcher m = pattern.matcher(resourceFile.getName()); if (m.find()) { String destinationNickname = m.group(1); String jobnumber = m.group(2); String originalFileName = m.group(3); }