具有多个退出点的代码段中的圈复杂度

I have this method that validates a password:

/**
 * Checks if the given password is valid.
 * 
 * @param password The password to validate.
 * @return {@code true} if the password is valid, {@code false} otherwise.
 */
public static boolean validatePassword(String password) {
    int len = password.length();
    if (len < 8 || len > 20)
        return false;
    boolean hasLetters = false;
    boolean hasDigits = false;
    for (int i=0; i<len; i++) {
        if (!Character.isLetterOrDigit(password.charAt(i)))
            return false;
        hasDigits = hasDigits || Character.isDigit(password.charAt(i));
        hasLetters = hasLetters || Character.isLetter(password.charAt(i));
    }
    return hasDigits && hasLetters;
}

让我们关注圈复杂度数:它的价值是什么?