Assignment: RestCountries

src/main/java/io/codelex/assignments/restcountries/Country.java

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+package io.codelex.assignments.restcountries;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class Country {
+    private final String name;
+    private String capital;
+    private int population;
+    private double area;
+    private Set<Currency> currencies = new HashSet<>();
+
+
+    public Country(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getCapital() {
+        return capital;
+    }
+
+    public void setCapital(String capital) {
+        this.capital = capital;
+    }
+
+    public int getPopulation() {
+        return population;
+    }
+
+    public void setPopulation(int population) {
+        this.population = population;
+    }
+
+    public double getArea() {
+        return area;
+    }
+
+    public void setArea(double area) {
+        this.area = area;
+    }
+
+    public Set<Currency> getCurrencies() {
+        return currencies;
+    }
+
+    public void addCurrency(Currency currency) {
+            currencies.add(currency);
+    }
+
+    public double getDensity() {
+        if (getPopulation() != 0 && getArea() != 0) {
+            return (getPopulation() / getArea());
+        }
+        return 0.0;
+    }
+
+    @Override
+    public String toString() {
+        return "Country{" +
+                "name='" + name + '\'' +
+                ", capital='" + capital + '\'' +
+                ", population=" + population +
+                ", area=" + area +
+                ", currencies=" + currencies +
+                '}';
+    }
+
+}

src/main/java/io/codelex/assignments/restcountries/Currency.java

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+package io.codelex.assignments.restcountries;
+
+import java.util.Objects;
+
+public class Currency {
+    private final String code;
+    private final String name;
+    private final String symbol;
+
+    public Currency(String code, String name, String symbol) {
+        this.code = code;
+        this.name = name;
+        this.symbol = symbol;
+    }
+
+    public String getCode() {
+        return code;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getSymbol() {
+        return symbol;
+    }
+
+    @Override
+    public String toString() {
+        return code + " \"" + name + "\" " + symbol;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        Currency currency = (Currency) o;
+
+        if (!Objects.equals(code, currency.code)) {
+            return false;
+        }
+        if (!Objects.equals(name, currency.name)) {
+            return false;
+        }
+        return Objects.equals(symbol, currency.symbol);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = code != null ? code.hashCode() : 0;
+        result = 31 * result + (name != null ? name.hashCode() : 0);
+        result = 31 * result + (symbol != null ? symbol.hashCode() : 0);
+        return result;
+    }
+
+}

src/main/java/io/codelex/assignments/restcountries/README.md

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+## Task
+---
+<br>
+<p>1. Using <a href="https://restcountries.eu">restcountries.eu</a> create a text data file in JSON format, containing only the
+following data about countries in the European Union: name, capital, currencies, population,
+area.</p>
+<br>
+<p>2. Read and process this file with your java program to get the following results:<br>
+<ol type="a">
+<li>top 10 countries with the biggest population</li>
+<li>top 10 countries with the biggest area</li>
+<li>top 10 countries with the biggest population density (people / square km)</li></ol></p><br>
+<p>3a. Add the ability to consume the data about countries directly from the <a href="https://restcountries.eu">restcountries.eu</a> and
+process it (keep the code that processes data from the text file as well!)<br>
+3b. Convert your application to Spring Boot application and expose results via REST API</p>
+4. Add unit tests<br><br>
+<b>Additional info:</b><br>
+1. and 2. are mandatory.<br>
+3a. and 3b. are very good to have, can be done in any order<br>
+4. is optional, but nice to have. do not be shy to try :)<br><br>
+<b>Deliverables:</b><br>
+1. source code<br>
+2. description how to run your program - i.e. how do you run it yourself. it might be using IDE, or
+a using command line, whatever works

src/main/java/io/codelex/assignments/restcountries/RestCountries.java

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+package io.codelex.assignments.restcountries;
+
+import org.json.JSONArray;
+import org.json.JSONObject;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+
+public class RestCountries {
+    public static void main(String[] args) throws IOException {
+        String jsonData = getRestCountriesJsonData();
+        List<Country> countries = parseRestCountriesJsonData(jsonData);
+
+        System.out.println("Top 10 by population:");
+        List<Country> top10pop = countries.stream()
+                                         .sorted(Comparator.comparing(Country::getPopulation).reversed())
+                                         .limit(10L)
+                                         .toList();
+        top10pop.forEach(System.out::println);
+
+        System.out.println();
+        System.out.println("Top 10 by area:");
+        List<Country> top10area = countries.stream()
+                                          .filter(country -> country.getArea() != 0)
+                                          .sorted(Comparator.comparing(Country::getArea).reversed())
+                                          .limit(10L)
+                                          .toList();
+        top10area.forEach(System.out::println);
+
+        System.out.println();
+        System.out.println("Top 10 by density");
+        List<Country> top10density = countries.stream()
+                                             .filter(country -> country.getDensity() != 0.0)
+                                             .sorted(Comparator.comparing(Country::getDensity).reversed())
+                                             .limit(10L)
+                                             .toList();
+        top10density.forEach(System.out::println);
+
+        System.out.println();
+        System.out.println("Listing all Countries");
+        countries.forEach(System.out::println);
+    }
+
+    private static String getLocalRestCountriesJsonData() throws IOException {
+        Path fileName = Path.of(Country.class.getResource("eu-countries.json").getPath());
+        return Files.readString(fileName);
+    }
+
+    private static String getRestCountriesJsonData() {
+        try {
+            URL url = new URL("https://restcountries.com/v2/regionalbloc/eu?fields=name,capital,currencies,population,area");
+            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
+            connection.setRequestMethod("GET");
+            connection.connect();
+            int responseCode = connection.getResponseCode();
+            if (responseCode != 200) {
+                throw new RuntimeException("HttpResponseCode: " + responseCode);
+            } else {
+                StringBuilder builder = new StringBuilder();
+                BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
+                String inputLine;
+                while ((inputLine = reader.readLine()) != null) {
+                    builder.append(inputLine);
+                }
+                return builder.toString();
+            }
+        } catch (Exception e) {
+            throw new RuntimeException(e.getMessage());
+        }
+    }
+
+    private static List<Country> parseRestCountriesJsonData(String jsonData) {
+        List<Country> countries = new ArrayList<>();
+        JSONArray jsonArr = new JSONArray(jsonData);
+        for (Object countryObj : jsonArr) {
+            JSONObject countryJson = (JSONObject) countryObj;
+            Country country = new Country(countryJson.getString("name"));
+            country.setCapital(countryJson.getString("capital"));
+            country.setPopulation(countryJson.getInt("population"));
+            if (countryJson.has("area")) {
+                country.setArea(countryJson.getDouble("area"));
+            }
+            for (Object currencyObj : countryJson.getJSONArray("currencies")) {
+                JSONObject currencyJson = (JSONObject) currencyObj;
+                String code = currencyJson.getString("code");
+                String name = currencyJson.getString("name");
+                String symbol = currencyJson.getString("symbol");
+                Currency currency = new Currency(code, name, symbol);
+                country.addCurrency(currency);
+            }
+            countries.add(country);
+        }
+        return countries;
+    }
+
+}