java string length validation regex
//Password validation example
public static Boolean validPassword(String password) throws IllegalArgumentException {
if (!password.matches("\w{6,}"))/*Or '(password.matches("\w{6,}") == false)'*/ {
throw new IllegalArgumentException("Password must be at least 6 characters long.");
//'("\w{int}")' => Must be int characters long.
//'("\w{int,}")' => Must be AT LEAST int characters long and can be longer.
//'("\w{int1,int2}")' => Must be BETWEEN int1 AND int2 characters long.
}
return true;
}