wiki.java

package no.statnett.ois;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;

public class WikipediaArticle {

    public static void main(String [] args) {
        System.out.println(topicCount("article"));
        System.out.println(topicCount("pizza"));
        System.out.println(topicCount("Pizza"));
        System.out.println(topicCount("MØ"));
        System.out.println(topicCount(""));
    }

    static int topicCount(String topic) {
        if (topic == null || topic.isEmpty()) {
            return 0;
        }
        URL wikiUrl = createWikiUrl(topic);
        String wikiContent = getContent(wikiUrl);
        int beginningOfArticle = findBeginningOfArticle(wikiContent);
        return countOccurrencesOfString(wikiContent, topic, beginningOfArticle);
    }

    private static URL createWikiUrl(final String topic) {
        try {
            return new URL(String.format("https://en.wikipedia.org/w/api.php?action=parse&section=0&prop=text&format=json&utf8&page=%s", URLEncoder.encode(topic, "UTF-8")));
        } catch (MalformedURLException | UnsupportedEncodingException e) {
            throw new RuntimeException("Error: Could not create url", e);
        }
    }

    private static String getContent(final URL url) {
        HttpURLConnection connection = null;
        BufferedReader bufferedReader = null;

        String content = "";
        try {
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            connection.connect();

            if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {

                BufferedInputStream bufferedInputStream = new BufferedInputStream(connection.getInputStream());
                bufferedReader = new BufferedReader(new InputStreamReader(bufferedInputStream, StandardCharsets.UTF_8));
                StringBuilder contentBuilder = new StringBuilder(content);

                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    contentBuilder.append(line);
                }
                content = contentBuilder.toString();
            }

        } catch (IOException e) {
            throw new RuntimeException("Error: Unable to get content", e);
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            try {
                if (bufferedReader != null) {
                    bufferedReader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return content;
    }

    private static int findBeginningOfArticle(final String wikiContent) {
        String beginningOfArticle = "\"text\":{\"*\":";
        int index = wikiContent.indexOf(beginningOfArticle);
        if (index != -1) {
            return index + beginningOfArticle.length();
        } else {
            return index;
        }
    }

    private static int countOccurrencesOfString(final String str, final String findStr, final int startingFromIndex) {
        int count = 0;
        int lastIndex = startingFromIndex;

        while (lastIndex != -1) {
            lastIndex = str.indexOf(findStr, lastIndex);
            if (lastIndex != -1) {
                count++;
                lastIndex += findStr.length();
            }
        }
        return count;
    }
}