Question

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
    at com.demo.parsing.MainActivity.main(MainActivity.java:47)

Writer out = new FileWriter(new File(args[0])); (line 47)

I am new to JAVA. I have been trying this code but not able to find what this arrayoutofboundexception. Here in this code i’m trying to parse some data from a local XML file and write it in a new file. The file is created but no text and getting the above exception

package com.demo.parsing;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.Writer;
import java.util.LinkedList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.jsoup.Jsoup;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
public class MainActivity {

//private static OutputStreamWriter out;


public static void main(String[] args) throws FileNotFoundException {
    FileInputStream f0 = new FileInputStream("/home/kailash/workspace/paarsing/pustaka-feed.xml");

    try {
        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();

        Document feed = builder.parse(f0);

        NodeList items = feed.getElementsByTagName("item");

        List<String> urls = new LinkedList<String>();

        for (int i = 0; i < items.getLength(); i++) {
            Element item = (Element) items.item(i);
            Element description = (Element) item.getElementsByTagName(
                    "description").item(0);
            urls.addAll(getImages(builder,    description.getTextContent()));
        }

 Writer out = new FileWriter(new File(args[0]));

        for (String url : urls) {
            out.write(url + "\n");
        }

        out.close();

    } catch (ParserConfigurationException e) {
        e.printStackTrace();
    } catch (SAXException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

private static List<String> getImages(DocumentBuilder builder, String content) throws SAXException, IOException {
    List<String> urls = new LinkedList<String>();

    for (org.jsoup.nodes.Element img :   Jsoup.parse(content).getElementsByTag("img")) {
        urls.add(img.attributes().get("src"));
    }

    return urls;
}
}

Answer 1

As you say you are newbie and dont know what ArrayIndexOutOfBoundsException is, Better read about ArrayIndexOutOfBoundsException , as this is one the most common exception you are going to face in future.

Now about your question, it is throwing a ArrayIndexOutOfBoundsException at line 47

As you point out , Line 47 is

    Writer out = new FileWriter(new File(args[0]));

See the exception trace carefully

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
    at com.demo.parsing.MainActivity.main(MainActivity.java:47)

The trace tells you

1. the exception : ArrayIndexOutOfBoundsException
2. idex at which this exception occurs : 0
3. line that is throwing the exception : MainActivity.java : 47 (that is why i asked what is line 47)

^telling above info as you are a newbie and this description might be helpful for you in near future.

So now comming back to your statement

Writer out = new FileWriter(new File(args[0]));

args[0] , it represents the command line arguments (see main method definition)

are you passing any command line arguments, when you are trying to run the application ?

To pass command line arguments

Through DOS : java nameofclassfile arg1 arg2 ......

Through Eclipse : right click java file -> run as-run configurations, in the dialog navigate to Arguments tab and enter your command line argument under the Program Arguments text Box and hit run