JAVASCRIPT

upi id regex

/^w.+@w+$/.test('rishi.21@axis')

/^w.+@w+$/.test('shruti@PNB')

/^w.+@w+$/.test('98765__210@upi')

upi id regex

public static boolean validateUPI(String upi){
        final Pattern VALID_EMAIL_ADDRESS_REGEX = Pattern.compile("^(.+)@(.+)$", Pattern.CASE_INSENSITIVE);
        Matcher matcher = VALID_EMAIL_ADDRESS_REGEX.matcher(upi);
        return matcher.find();
}