Programming Forums > Application Development > Java

Eric the Red · Jun 23rd, 2006, 9:47 AM

Previously, I made a post because I had an error in one of my programs. I wasn't too sure what the problem was so I made many different posts in my thread. Now I brought this down to one problem .

For some reason the code below works. However, making an object out of this class doesn't.

This works alone without any errors:

(Toggle Plain Text)

import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;

public class ReadFile extends javax.swing.JApplet //Applet
{

    StringBuffer buf;
    String FileToRead = "testFile.txt";
    String fileData [] = new String [1];
    int countLines = 2;


    //--------------------------------------------------------
    public void init ()
    {
    //public ReadFile (URL codebase)
    //{

        String line;
        URL url = null;

        try
        {
            //System.out.println ("" + getCodeBase ());
           url = new URL (getCodeBase (), FileToRead);
           //url = new URL (codebase, FileToRead); 
        }
        catch (MalformedURLException e)
        {
            System.out.println ("Malformed URL ");
            stop ();
        }

        try
        {
            InputStream in = url.openStream ();
            BufferedReader dis = new BufferedReader (new InputStreamReader (in)); // check number of lines

            buf = new StringBuffer ();
            countLines = 0;

            while ((line = dis.readLine ()) != null)
            {
                countLines = countLines + 1;
            }
            in.close ();
           
            dis.close ();

            fileData = new String [countLines];
           
            in = url.openStream ();
            dis = new BufferedReader (new InputStreamReader (in)); // now read the file

           

            for (int v = 0 ; v < countLines ; v++)
            {
                fileData [v] = dis.readLine ();
              
            }
            dis.close ();
            
        }
        catch (IOException e)
        {
        }
        // Load the file into the TextArea.
        //ta.append(buf.toString ());

        repaint ();
    }


    public void paint (Graphics screen)
     {


         {
             Graphics2D screen2D = (Graphics2D) screen;
             String tempStr = buf.toString ();

             //screen2D.drawString (tempStr, 10, 10);
             for (int q = 0 ; q < countLines ; q++)
             {
                 screen2D.drawString (fileData [q], 10, 10 + q * 15);
             }

         }
     } 

    int getLines ()
    {
        return countLines;
    }


    String getData ()
    {
        return fileData [1];
    }


    int getInt ()
    {
        return countLines;
    }
}

import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;

public class ReadFile extends javax.swing.JApplet //Applet
{

    StringBuffer buf;
    String FileToRead = "testFile.txt";
    String fileData [] = new String [1];
    int countLines = 2;


    //--------------------------------------------------------
    public void init ()
    {
    //public ReadFile (URL codebase)
    //{

        String line;
        URL url = null;

        try
        {
            //System.out.println ("" + getCodeBase ());
           url = new URL (getCodeBase (), FileToRead);
           //url = new URL (codebase, FileToRead); 
        }
        catch (MalformedURLException e)
        {
            System.out.println ("Malformed URL ");
            stop ();
        }

        try
        {
            InputStream in = url.openStream ();
            BufferedReader dis = new BufferedReader (new InputStreamReader (in)); // check number of lines

            buf = new StringBuffer ();
            countLines = 0;

            while ((line = dis.readLine ()) != null)
            {
                countLines = countLines + 1;
            }
            in.close ();
           
            dis.close ();

            fileData = new String [countLines];
           
            in = url.openStream ();
            dis = new BufferedReader (new InputStreamReader (in)); // now read the file

           

            for (int v = 0 ; v < countLines ; v++)
            {
                fileData [v] = dis.readLine ();
              
            }
            dis.close ();
            
        }
        catch (IOException e)
        {
        }
        // Load the file into the TextArea.
        //ta.append(buf.toString ());

        repaint ();
    }


    public void paint (Graphics screen)
     {


         {
             Graphics2D screen2D = (Graphics2D) screen;
             String tempStr = buf.toString ();

             //screen2D.drawString (tempStr, 10, 10);
             for (int q = 0 ; q < countLines ; q++)
             {
                 screen2D.drawString (fileData [q], 10, 10 + q * 15);
             }

         }
     } 

    int getLines ()
    {
        return countLines;
    }


    String getData ()
    {
        return fileData [1];
    }


    int getInt ()
    {
        return countLines;
    }
}

Now that works, please feel free to download the .zip containning the html file + the txt file so you can compile this.

The above works without any errors what so ever. So why doesn't the below code work? I seem to get an error at the "getCodeBase()" command whenever the class above becomes a helper class to another class such as "MainClass.java".

Here's what I mean, below MainSomething.java is creating a FileRead Object. However, now the "getCodeBase()" is popping up as an error. Which wasn't an issue until I made it a helper class.

(Toggle Plain Text)

//MainSomething.java
import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;

class MainSomething extends Applet
{
    ReadFile testing;
    int tempInt = 1;
    StringBuffer buf;
    int something = 1;
    String fileDat = new String ();
    public void init ()
    {
        //ReadFileTemp testing = new ReadFileTemp ();
        ReadFile testing = new ReadFile ();
        something = testing.getLines();
        //repaint (
        //buf = testing.getBuf();
        fileDat = testing.getData();
        tempInt = testing.getInt ();
        repaint ();
    }


    public void paint (Graphics screen)
    {
        Graphics2D screen2D = (Graphics2D) screen;

        screen2D.drawString ("hello", 10, 20);

        screen2D.drawString (something + "", 10, 50);
        screen2D.drawString ((tempInt + ""), 10, 30);
        screen2D.drawString (( fileDat + ""), 10, 80);
    }
}
// end of SomethingMain.class
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
//ReadFile.class
import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;

public class ReadFile extends javax.swing.JApplet //Applet
{

    StringBuffer buf;
    String FileToRead = "testFile.txt";
    String fileData [] = new String [1];
    int countLines = 2;


    //--------------------------------------------------------
    //public void init ()
    //{
    public ReadFile ()
    {

        String line;
        URL url = null;

        try
        {
            //System.out.println ("" + getCodeBase ());
           url = new URL (getCodeBase (), FileToRead); // error
           //url = new URL (codebase, FileToRead); 
        }
        catch (MalformedURLException e)
        {
            System.out.println ("Malformed URL ");
            stop ();
        }

        try
        {
            InputStream in = url.openStream ();
            BufferedReader dis = new BufferedReader (new InputStreamReader (in)); // check number of lines

            buf = new StringBuffer ();
            countLines = 0;

            while ((line = dis.readLine ()) != null)
            {
                countLines = countLines + 1;
            }
            in.close ();
           
            dis.close ();

            fileData = new String [countLines];
           
            in = url.openStream ();
            dis = new BufferedReader (new InputStreamReader (in)); // now read the file

           

            for (int v = 0 ; v < countLines ; v++)
            {
                fileData [v] = dis.readLine ();
              
            }
            dis.close ();
            
        }
        catch (IOException e)
        {
        }
        // Load the file into the TextArea.
        //ta.append(buf.toString ());

        repaint ();
    }

    int getLines ()
    {
        return countLines;
    }


    String getData ()
    {
        return fileData [1];
    }


    int getInt ()
    {
        return countLines;
    }
}
// testFile.txt
banhkshkaj
hadsljaljdas
ashdfjskdahl
boom

//MainSomething.java
import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;

class MainSomething extends Applet
{
    ReadFile testing;
    int tempInt = 1;
    StringBuffer buf;
    int something = 1;
    String fileDat = new String ();
    public void init ()
    {
        //ReadFileTemp testing = new ReadFileTemp ();
        ReadFile testing = new ReadFile ();
        something = testing.getLines();
        //repaint (
        //buf = testing.getBuf();
        fileDat = testing.getData();
        tempInt = testing.getInt ();
        repaint ();
    }


    public void paint (Graphics screen)
    {
        Graphics2D screen2D = (Graphics2D) screen;

        screen2D.drawString ("hello", 10, 20);

        screen2D.drawString (something + "", 10, 50);
        screen2D.drawString ((tempInt + ""), 10, 30);
        screen2D.drawString (( fileDat + ""), 10, 80);
    }
}
// end of SomethingMain.class
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
//ReadFile.class
import java.applet.*;
import java.awt.*;
import java.io.*;
import java.net.*;

public class ReadFile extends javax.swing.JApplet //Applet
{

    StringBuffer buf;
    String FileToRead = "testFile.txt";
    String fileData [] = new String [1];
    int countLines = 2;


    //--------------------------------------------------------
    //public void init ()
    //{
    public ReadFile ()
    {

        String line;
        URL url = null;

        try
        {
            //System.out.println ("" + getCodeBase ());
           url = new URL (getCodeBase (), FileToRead); // error
           //url = new URL (codebase, FileToRead); 
        }
        catch (MalformedURLException e)
        {
            System.out.println ("Malformed URL ");
            stop ();
        }

        try
        {
            InputStream in = url.openStream ();
            BufferedReader dis = new BufferedReader (new InputStreamReader (in)); // check number of lines

            buf = new StringBuffer ();
            countLines = 0;

            while ((line = dis.readLine ()) != null)
            {
                countLines = countLines + 1;
            }
            in.close ();
           
            dis.close ();

            fileData = new String [countLines];
           
            in = url.openStream ();
            dis = new BufferedReader (new InputStreamReader (in)); // now read the file

           

            for (int v = 0 ; v < countLines ; v++)
            {
                fileData [v] = dis.readLine ();
              
            }
            dis.close ();
            
        }
        catch (IOException e)
        {
        }
        // Load the file into the TextArea.
        //ta.append(buf.toString ());

        repaint ();
    }

    int getLines ()
    {
        return countLines;
    }


    String getData ()
    {
        return fileData [1];
    }


    int getInt ()
    {
        return countLines;
    }
}
// testFile.txt
banhkshkaj
hadsljaljdas
ashdfjskdahl
boom

If you can't see the error easily, please download the .zip. For, it contains everything needed to test it out.

jaeusm · Jun 23rd, 2006, 12:32 PM

I can't download and compile this at work (we only develop .NET), so what is the actual error message?

Eric the Red · Jun 23rd, 2006, 1:15 PM

Quote:

Originally Posted by jaeusm

I can't download and compile this at work (we only develop .NET), so what is the actual error message?

(Toggle Plain Text)

java.lang.NullPointerException
        at java.applet.Applet.getCodeBase(Applet.java:136)
        at ReadFile.<init>(ReadFile.java:27)
        at MainSomething.init(MainSomething.java:16)
        at ready.AppletRunner.run(AppletRunner.java:209)
        at java.lang.Thread.run(Thread.java:536)

Eric the Red · Jun 24th, 2006, 5:13 PM

Does anyone know? Anything would help me really. Maybe I'm not able to use "getCodeBase()" in a helper class. Does that sound realistic?

Arevos · Jun 24th, 2006, 6:24 PM

Quote:

Originally Posted by Eric the Red

Here's what I mean, below MainSomething.java is creating a FileRead Object. However, now the "getCodeBase()" is popping up as an error. Which wasn't an issue until I made it a helper class.

Presumably, the code base is supplied to an applet by the presiding JVM. If an applet is constructed manually, it doesn't appear to have access to the same information.

You could try overriding getCodeBase to return a fixed URL, or have the code base URL passed to it by its initiating class. You probably shouldn't inherit from JApplet for a helper class, either. It doesn't strike me as very modular design.

Eric the Red · Jun 24th, 2006, 10:01 PM

Quote:

Originally Posted by Arevos

Presumably, the code base is supplied to an applet by the presiding JVM. If an applet is constructed manually, it doesn't appear to have access to the same information.

You could try overriding getCodeBase to return a fixed URL, or have the code base URL passed to it by its initiating class. You probably shouldn't inherit from JApplet for a helper class, either. It doesn't strike me as very modular design.

Thx, for your help!!! Okayy, I tried sending in the URL from the calling class and it now works.

Why would you say that inheritting from a JAPPLET for a helper class is wrong though? Please expand on that. It might prevent a lot of problems in the future.

Jun 24th, 2006, 5:13 PM	#4
Eric the Red Hobbyist Programmer Join Date: Feb 2006 Posts: 214 Rep Power: 0	Does anyone know? Anything would help me really. Maybe I'm not able to use "getCodeBase()" in a helper class. Does that sound realistic? __________________ Death smiles at us all. All a man can do is smile back.

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Jun 23rd, 2006, 12:32 PM	#2
jaeusm Programmer Join Date: Feb 2006 Location: Columbus, OH Posts: 84 Rep Power: 3	I can't download and compile this at work (we only develop .NET), so what is the actual error message?

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Programming Forums > Application Development > Java

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