need help with exception

[neha gautam]

hi all, i m gettin a null pointer exception in this, in line 28,43, 56, , but i m not able figure it out please help
code is

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.BoxLayout;
import javax.swing.ButtonGroup;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;

public class UI extends JPanel
{
	private JRadioButton[] files = null;
	private JScrollPane scrollPane;
	private JPanel radioButtonPanel;
	private JPanel actionPanel;
	private BoxLayout layout;
	private ButtonGroup group;
	
	public UI()
	{
		radioButtonPanel = new JPanel();
		
		layout = new BoxLayout(radioButtonPanel, BoxLayout.Y_AXIS);
		radioButtonPanel.setLayout(layout);
		group = new ButtonGroup();
		
		updateRadioButtonPanel();
		
		scrollPane = new JScrollPane(radioButtonPanel);
		scrollPane.setPreferredSize(new Dimension(400,300));
		
		add(scrollPane, BorderLayout.CENTER);
		
		actionPanel = new JPanel();
		
		add(actionPanel, BorderLayout.SOUTH);
	}
	
	public void updateRadioButtonPanel()     // gettin exception
	{
		String[] fileNames = DirectoryTest.getFilesInDir("C:\neha\files");
		files = new JRadioButton[fileNames.length];
		for(int i = 0; i < fileNames.length; i++)
		{
			files[i] = new JRadioButton(fileNames[i]);
			group.add(files[i]);
			radioButtonPanel.add(files[i]);
		}
		radioButtonPanel.repaint();
	}
	
	public static void main(String[] args)
	{
		JFrame f = new JFrame();
		UI ui = new UI();
		f.setContentPane(ui);
		f.pack();
		f.setVisible(true);
	}	
}
	


import java.io.File;
import java.util.Arrays;

public class DirectoryTest
{
	public static String[] getFilesInDir(String dir)
	{
		String[] filesInDir = null;
		if(dir != null && !dir.equals(""))
		{
			// create a file that is really a directory
			File aDirectory = new File(dir);
			
			if(aDirectory.isDirectory())
			{
				// get a listing of all files in the directory
				filesInDir = aDirectory.list();
				
				// sort the list of files (optional)
				Arrays.sort(filesInDir);

				// have everything i need, just print it now, 
				for ( int i=0; i<filesInDir.length; i++ )
				{
					System.out.println( "file: " + filesInDir[i] );
				}
			}
		}
		
		return filesInDir;
	}	
	public static void main(String[] args)
	{
		if(args.length > 0)
			getFilesInDir(args[0]);
		else
			getFilesInDir("C:\neha");
	}		
}

thanks to all

[Swastik Dey]

C:\neha\files

\ is an escape character in java, so in this case you need

C:\\neha\\files

and same for getFilesInDir("C:\\neha"); in DirectoryTest.java

now even if you specify the correct path its possible that no files exist in the specified in the given directory , so you need to put check before continuing the process

 
public void updateRadioButtonPanel() // gettin exception
{
String[] fileNames = DirectoryTest.getFilesInDir("C:\\neha\\files");
//lets put a check below that the array isnot null and length is >0
if(fileNames==null || fileNames.length==0){
	JOptionPane.showMessageDialog(this,"Failed to load files from directory");
	return;
}
files = new JRadioButton[fileNames.length];
for(int i = 0; i < fileNames.length; i++)
{
files[i] = new JRadioButton(fileNames[i]);
group.add(files[i]);
radioButtonPanel.add(files[i]);
}
radioButtonPanel.repaint();
}
   

[Maneesh Godbole]

Neha,
In future, please use code tags.
I have edited your original post to use code tags, and as you can see it makes the code easier to read an understand. It even displays the line numbers !

[neha gautam]

got it!!!
thank a ton

[neha gautam]

roger maneesh thanks