import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import static java.util.Arrays.asList;

public class Regex3 {
    private static final String EMAIL_REGEX = "(\\w+\\.\\w+|\\w+)(\\+\\w+)?@hogwarts(\\.\\w{2,3})+";

    public static void main(String[] args) {
        Regex3 regex = new Regex3();
        regex.shouldMatchEmailRegex();
    }

    private void shouldMatchEmailRegex() {
        List<String> shouldMatch = asList("tom@hogwarts.com", "tom.riddle@hogwarts.com",
                "tom.riddle+regexone@hogwarts.com", "tom@hogwarts.eu.com", "potter@hogwarts.com", "harry@hogwarts.com",
                "hermione+regexone@hogwarts.com");
        List<String> captureGroups = asList("tom", "tom.riddle", "tom.riddle", "tom", "potter", "harry", "hermione");

        shouldMatchRegexAndCaptures(EMAIL_REGEX, shouldMatch, captureGroups);
    }

    private void shouldMatchRegexAndCaptures(String regex, List<String> shouldMatch, List<String> captureGroups) {
        for (int i = 0; i < shouldMatch.size(); i++) {
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(shouldMatch.get(i));
            if (!matcher.matches()) {
                throw new IllegalStateException(shouldMatch.get(i) + " - Should match regex!");
            }
            if (!matcher.group(1).equals(captureGroups.get(i))) {
                throw new IllegalStateException(
                        shouldMatch.get(i) + " - Should match - " + captureGroups.get(i) + " - capture group!");
            }
        }
    }
}