import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Example {
public static void main(String[] args) {
final String regex = "^(?=.{1,39}$)^[a-zA-Z\\d]+(?:-[a-zA-Z\\d]+)*$";
final String string = "-username\n"
+ "_username_\n"
+ "__us_ername\n"
+ "us_er\n"
+ "username-\n"
+ "1user--name\n"
+ "132uname-\n"
+ "-uname1234\n"
+ "-username-\n"
+ "user--name\n"
+ "av34axc-\n"
+ "1234567890A1234567890B1234567890C1234567890D\n\n"
+ "Username\n"
+ "a-a\n"
+ "aBc\n"
+ "BaC\n"
+ "1-1\n"
+ "1-2-3-4\n"
+ "q-1-2-3\n"
+ "q-q-q-q-q\n"
+ "username\n"
+ "123username123\n"
+ "username3123\n"
+ "1234\n"
+ "user-name\n"
+ "13-13\n"
+ "q1-q2-q3\n"
+ "a\n"
+ "A\n"
+ "1234567890A1234567890B1234567890C123456\n"
+ "1234567890A123456-7890B1234567890C12345";
final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
final Matcher matcher = pattern.matcher(string);
while (matcher.find()) {
System.out.println("Full match: " + matcher.group(0));
for (int i = 1; i <= matcher.groupCount(); i++) {
System.out.println("Group " + i + ": " + matcher.group(i));
}
}
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html