How to make an easy cantor with regex-CodePudding

I want to create a method that will change values like in cantor. I have String :

String rates = "{\"rates\":{\"CAD\":1.5563,\"HKD\":9.1212,\"ISK\":162.6,\"PHP\":57.324,\"DKK\":7.4441,\"HUF\":350.68,\"CZK\":26.083,\"AUD\":1.6442,"
                   "\"RON\":4.8405,\"SEK\":10.363,\"IDR\":17383.99,\"INR\":88.198,\"BRL\":6.5908,\"RUB\":87.735,\"HRK\":7.5243,\"JPY\":124.53,\"THB\":37.161,"
                   "\"CHF\":1.0744,\"SGD\":1.6131,\"PLN\":4.3979,\"BGN\":1.9558,\"TRY\":8.5925,\"CNY\":8.1483,\"NOK\":10.5913,\"NZD\":1.8045,\"ZAR\":20.2977,"
                   "\"USD\":1.1769,\"MXN\":26.066,\"ILS\":4.0029,\"GBP\":0.89755,\"KRW\":1403.15,\"MYR\":4.9194},\"base\":\"EUR\",\"date\":\"2020-08-21\"}";

I want to create method :

public double change(int value, String country) {

so if I use method like: change(100, "PLN") it should give me : 439.79

I tried to think about using Pattern, but I dont know how to put my parameter String in regex.

I tried something like this :

Pattern pattern = Pattern.compile("(?<country>\"([A-Z]){3}\"):(?<rate>[0-9] \\.[0-9] )");

CodePudding user response：

I write a method :

public static double zamien(int ilosc, String waluta, String kursy) {
        double result = 0.0;

        Pattern pattern = Pattern.compile("(?<kraj>([A-Z]){3}\"):(?<kurs>[0-9] \\.[0-9] )");

        if(!kursy.contains(waluta)) {
            throw new IllegalArgumentException("Nie ma takiej waluty!");
        }

        int firstIndex = kursy.indexOf(waluta);
        String krajIkurs = kursy.substring(firstIndex, firstIndex   11);
        //System.out.println(krajIkurs);

        Matcher matcher = pattern.matcher(krajIkurs);


        if (matcher.matches()) {
            double rate = Double.parseDouble(matcher.group("kurs"));
            result = ilosc * rate;
        } else {
            throw new IllegalArgumentException("zly pattern!");
        }

        return result;

    }

It works good for me but Can I do it better?

CodePudding user response：

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class CurrencyConverter {
    private static String rates = "{\"rates\":{\"CAD\":1.5563,\"HKD\":9.1212,\"MYR\":4.9194},\"base\":\"EUR\",\"date\":\"2020-08-21\"}";
private static JsonNode root;

static {
    try {
        root = new ObjectMapper().readTree(rates);
    } catch (Exception e) {
        throw new RuntimeException("Error while parsing rates JSON string", e);
    }
}

public static double change(int value, String country) throws Exception {
    JsonNode ratesNode = root.path("rates");
    if (!ratesNode.has(country)) {
        throw new Exception("Country not found in rates");
    }

    double rate = ratesNode.get(country).asDouble();
    return value * rate;
}

}