Regex Hello World..

.. with Java Standard Library!

RegexHello.java
import java.util.regex.Pattern;
import java.util.regex.Matcher;
 
public class RegexHello {
 
    public static void main(String[] args) {
        final String phoneNumberRegex = "((\\d){3}-(\\d){1,4})";
        final String haysack = "454-3fdasfr456-324fasadfad454-431312343-43dsfafads";
        final Pattern phoneNumberPattern = Pattern.compile(phoneNumberRegex);
        final Matcher matcher = phoneNumberPattern.matcher(haysack);
        while(matcher.find()) {
            System.out.println(matcher.start() + "\t- " + matcher.group());
        }
    }
}

And the output is..
0      - 454-3
11     - 456-324
26     - 454-4313
36     - 343-43