[SOLVED] java.lang.NullPointerException when reading getClass().getResourceAsStream(.

[jon80]

The code below is generating an error when trying to read a stream object (see code). The file is located within a subdirectory named 'config' in the sub-folder of the project.

:confused:

package homenetwork.bkr.training;
import java.awt.*;
import java.io.*;
import java.net.URL;
import java.util.*;
import javax.swing.*;

@SuppressWarnings("serial")
public class ResourceTestFrame extends JFrame {
	
	public ResourceTestFrame() {
			setTitle("Resource Test");
			setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
			URL aboutURL = getClass().getResource("icons/exit.png");
			Image img = Toolkit.getDefaultToolkit().getImage(aboutURL);
			setIconImage(img);
			
			JTextArea textArea = new JTextArea();
			//InputStream stream = getClass().getResourceAsStream("config/about.txt");  //Option A

			[B]InputStream stream = getClass().getResourceAsStream("C:\\config\\about.txt"); //Option B[/B]
			Scanner in = new Scanner(stream);
			Scanner in = new Scanner(stream);
			while (in.hasNext())
				textArea.append(in.nextLine() + "\n");
			
			add(textArea);
	}
	
	public static final int DEFAULT_WIDTH = 300;
	public static final int DEFAULT_HEIGHT =300;
	
}

Error:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.io.Reader.<init>(Unknown Source)
at java.io.InputStreamReader.<init>(Unknown Source)
at java.util.Scanner.<init>(Unknown Source)
at homenetwork.bkr.training.ResourceTestFrame.<init>( ResourceTestFrame.java:21)
at homenetwork.bkr.training.ResourceTest$1.run(Resour ceTest.java:13)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[hardwired]

This worked okay: Both the image and the source/.java file appeared in the gui.
The console output was:

C:\jexp>java RTF
url = file:/C:/jexp/images/dukeWaveRed.gif

import java.awt.*;
import java.io.InputStream;
import java.net.URL;
import java.util.Scanner;
import javax.swing.*;

public class RTF extends JFrame {

    public RTF() {
        super("Resource Test");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
        URL url = getClass().getResource(//"icons/exit.png");
                                         "images/dukeWaveRed.gif");
        System.out.println("url = " + url);
        Image img = Toolkit.getDefaultToolkit().createImage(url);
        add(new JLabel(new ImageIcon(img)), "First");

        JTextArea textArea = new JTextArea();
        InputStream stream =                     //Option A
            getClass().getResourceAsStream(//"config/about.txt");
                                           "utilities/FileSize.java");

        //InputStream stream =                   //Option B
        //    getClass().getResourceAsStream("C:\\config\\about.txt");
        Scanner in = new Scanner(stream);
        while (in.hasNext())
            textArea.append(in.nextLine() + "\n");

        add(new JScrollPane(textArea));
        setVisible(true);
    }

    public static void main(String[] args) { new RTF(); }

    public static final int DEFAULT_WIDTH = 300;
    public static final int DEFAULT_HEIGHT =300;
}

InputStream stream =                     //Option A
    getClass().getResourceAsStream(//"config/about.txt");
                                   "utilities/FileSize.java");

The utilities folder is located in the same folder as the class file, the current directory, and it contains a file named FileSize.java.

InputStream stream =                   //Option B
    getClass().getResourceAsStream("C:\\config\\about.txt");

With the argument "C:\\config\\about.txt" the class loader will look in the C folder for a folder called config and inside it will be a file named about.txt.
The file is located within a subdirectory named 'config' in the sub-folder of the project.
A sub-folder of the project...
If the project is in the C folder then it contains a sub-folder which then contains the config folder. The class loader won't be looking for the extra folder between C and config.
Try a path relative to your class file. If the class file is in the project folder you can try:

// The project folder is the current directory and contains the class file
// and also contains a folder named [i]subFolder[/i].
getResourceAsStream("subFolder/config/about.txt");

You can use a single forward slash for file separator for/in java.

[jon80]

Thanks. My mistake was not having included the sub-folders under the package name.

C:\Users\Administrator\workspace\ResourceTestTwo>t ree /F /a
NOTE: It's noted that somehow a space is inserted between the 't' and the 'r' when I select 'Save' :S
Folder PATH listing
Volume serial number is 982D-F9F4
C:.
| .classpath
| .project
|
+---.settings
| org.eclipse.jdt.core.prefs
|
+---bin
| \---homenetwork
| \---bkr
| \---training
| | RTF.class
| |
| +---config
| | about.txt
| |
| \---images
| car.jpg
|
\---src
\---homenetwork
\---bkr
\---training
| RTF.java
|
+---config
| about.txt
|
\---images
car.jpg