Dumbfounded by Scanner processing String using regular expression

Question

I was reading Bruce Eckel's book when I came across something interesting: extending Scanner with regular expressions. Unfortunately, I was confronted with an issue that doesn't make much sense to me: if the String that I am scanning contains a hyphen, the Scanner doesn't produce anything. As soon as I take it out, it all works like a charm. Here is my example:
import java.util.Scanner;
import java.util.regex.*;
public class StringScan {
public static void main (String [] args){
     String input = "there's one caveat when scanning with regular expressions";
     Scanner scanner = new Scanner (input);
     String pattern = "[a-z]\\w+";
     while (scanner.hasNext(pattern)){
          scanner.next(pattern);
          MatchResult match = scanner.match();
          String output = match.group();
          System.out.println(output);
}What could be the reason? I imagined it could be because the hyphen for some reason gets given a special meaning but when I tried escaping it, it still didn't work.

Answer 1

Thanks for your prompt reply.
I have figured out what was wrong with my code, by the way. Since a single quote is not a word character, it does not match w+. And as the very first input token does not match, the scanner stops immediately. I rewrote my regex to "[a-z].*" and now it does work.