18.zadatak

public static String normalizePhoneNumber(String phoneNumber) throws NumberFormatException{
        String allowedChar = "0123456789 /()";
        if(phoneNumber.isEmpty()){
            throw new NumberFormatException("Invalid Number");
        }
        for(char i : phoneNumber.toCharArray()){
            if(allowedChar.indexOf(i) == -1){
                throw new NumberFormatException("Invalid Number");
            }
        }
        String newPhoneNumber = phoneNumber.replaceAll("[()/ ]", "");
        if(newPhoneNumber.startsWith("00")){
            newPhoneNumber = newPhoneNumber.replaceFirst("00","+");
        }
        else if(newPhoneNumber.startsWith("0")){
            newPhoneNumber = newPhoneNumber.replaceFirst("0","+385");
        }

        return newPhoneNumber;
    }