NullPointerException

[Eleeist]

Hello,

I am trying to read data from XML file. I have trouble returning the data that was read.

Here is the error the I get:

java.lang.NullPointerException
    at AccountStatus.getAccountStatus(AccountStatus.java:35)
    at Program.main(Program.java:12)
Exception in thread "main" java.lang.NullPointerException
    at Program.main(Program.java:14)
Java Result: 1

Here is the AccountStatus.class:

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Node;
import org.w3c.dom.Element;
import java.net.URL;
import java.util.ArrayList;
 
public class AccountStatus {
    
    private ArrayList<String> accountStatusData;
    
    public ArrayList<String> getAccountStatus() {

        try {
            
            UserData userdata = new UserData();
            ReadData readdata = new ReadData();

            DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
            DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
            Document doc = dBuilder.parse(new URL(myurl);
            doc.getDocumentElement().normalize();
            NodeList nList = doc.getElementsByTagName("result");
            
            for (int temp = 0; temp < nList.getLength(); temp++) {

                Node nNode = nList.item(temp);
                
                if (nNode.getNodeType() == Node.ELEMENT_NODE) {

                    Element eElement = (Element) nNode;
                    
                    accountStatusData.add(readdata.getTagValue("paidUntil", eElement));
                    accountStatusData.add(readdata.getTagValue("createDate", eElement));
                    accountStatusData.add(readdata.getTagValue("logonCount", eElement));
                    accountStatusData.add(readdata.getTagValue("logonMinutes", eElement));

                }
                
            }
            
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        return accountStatusData;
                
    }
    
}

And this is Program.class:

import java.util.ArrayList;

public class Program {

    public static void main(String[] args) {

        ArrayList<String> myArrayList;
        
        AccountStatus accountStatus = new AccountStatus();
        
        myArrayList = accountStatus.getAccountStatus();
        
        Object o = myArrayList.get(0);
        
        System.out.println(o);
       
    }

}

Whis is it nor working?

[pbrockway2]

java.lang.NullPointerException
    at AccountStatus.getAccountStatus(AccountStatus.java:35)

You are using a variable (or expression) on this line as if it had a non null value when it is really null. Typical examples of this are using the dot operator or accessing array elements.

String[] foo;
foo[0] = "bar";  // bad! foo is null

foo = new String[42];
foo[10].length(); // bad! foo[10] is null

The line in question - line 35 of AccountStatus.java - is this one (I think):

accountStatusData.add(readdata.getTagValue("paidUntil", eElement));

There are two things you are relying on on this line to have nonnull values: accountStatusData and readdata. And one of them is null. The first thing to do is find out which. You can do this by using System.out.println().

System.out.println("About to add account status data");
System.out.println("accountStatusData=" + accountStatusData + "  readdata=" + readdata);
accountStatusData.add(readdata.getTagValue("paidUntil", eElement));

Once you have found out which variable is null go back through your code to where you thought you had given the variable a nonnull value and figure out why that didn't happen.

[Eleeist]

Problem solved. Thanks :).

[pbrockway2]

You're welcome.