URL连接上的InputStreamReader返回null

Question

I am following a tutorial on web scraping from the book "Web Scraping with Java". The following code gives me a nullPointerExcpetion. Part of the problem is that (line = in.readLine()) is always null, so the while loop at line 33 never runs. I do not know why it is always null however. Can anyone offer me insight into this? This code should print the first paragraph of the wikipedia article on CPython.

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import java.net.*;
import java.io.*;

public class WikiScraper {
    public static void main(String[] args) {
        scrapeTopic("/wiki/CPython");
    }
    public static void scrapeTopic(String url){
        String html = getUrl("http://www.wikipedia.org/"+url);
        Document doc = Jsoup.parse(html);
        String contentText = doc.select("#mw-content-text > p").first().text();
        System.out.println(contentText);
    }
    public static String getUrl(String url){
        URL urlObj = null;
        try{
            urlObj = new URL(url);
        }
        catch(MalformedURLException e){
            System.out.println("The url was malformed!");
            return "";
        }
        URLConnection urlCon = null;
        BufferedReader in = null;
        String outputText = "";
        try{
            urlCon = urlObj.openConnection();
            in = new BufferedReader(new InputStreamReader(urlCon.getInputStream()));
            String line = "";
            while((line = in.readLine()) != null){
                outputText += line;
            }
            in.close();
        }catch(IOException e){
            System.out.println("There was an error connecting to the URL");
            return "";
        }
        return outputText;
    }
}

Answer 1

If you enter http://www.wikipedia.org//wiki/CPython in web browser, it will be redirected to https://en.wikipedia.org/wiki/CPython , so

use String html = getUrl("https://en.wikipedia.org/"+url);

instead String html = getUrl("http://www.wikipedia.org/"+url);

then line = in.readLine() can really read something.