Question

String input = "2012 AL REG TEXT 300535(NS)";
String regex = "^((\\d{4})\\s+)?((\\S+)\\s+(.+?)\\s+)\\s+((\\S+)(\\s+\\(.*?\\)))$";

I want to capture 2012 in a group, “AL REG TEXT” in another group, and “300535(NS)” in another group.

Answer 1

The error is that you have an extra \\s+ right before the expected parantheses and, as @cmonkey points out, an extra \\s+ in the middle. Remove these and it works. Also, to only get the groups you mention above, add ?: to the ones you don’t want to capture:

String input = "2012 AL REG TEXT 300535(NS)";
String regex = "^(?:(\\d{4})\\s+)?((?:\\S+)\\s+(?:.+?))\\s+((?:\\S+)(?:\\(.*?\\)))$";
Matcher m = Pattern.compile(regex).matcher(input);
if (m.matches()) {
    for (int i = 1; i <= m.groupCount(); i++) {
        System.out.format("Group %d: '%s'%n", i, m.group(i));
    }
}

prints

Group 1: '2012'
Group 2: 'AL REG TEXT'
Group 3: '300535(NS)'