Directory scan NullPointer results in error (sometimes)

Question

Could somebody explain the flowing error to me please:
Exception in thread "Basic L&F File Loading Thread" java.lang.NullPointerException
statistics.pass1.xml
        at java.util.Arrays$ArrayList.<init>(Arrays.java:3357)
        at java.util.Arrays.asList(Arrays.java:3343)
        at sun.awt.shell.Win32ShellFolderManager2.isFileSystemRoot(Win32ShellFolderManager2.java:358)
        at sun.awt.shell.ShellFolder.isFileSystemRoot(ShellFolder.java:242)
        at javax.swing.filechooser.FileSystemView.isFileSystemRoot(FileSystemView.java:323)
        at javax.swing.filechooser.FileSystemView.getShellFolder(FileSystemView.java:531)
statistics.xml
        at javax.swing.filechooser.FileSystemView.getFiles(FileSystemView.java:443)
        at javax.swing.plaf.basic.BasicDirectoryModel$LoadFilesThread.run0(BasicDirectoryModel.java:218)
        at javax.swing.plaf.basic.BasicDirectoryModel$LoadFilesThread.run(BasicDirectoryModel.java:211)
BUILD SUCCESSFUL (total time: 6 seconds)The error is basically always the same, but I don't always get the errors.
When I run the directory scanner on (for example) my c:\ drive it runs without problems. But in some folders it gives me the errors above but I don't see why. They both have files and folders in it so I don't see the difference.
The same with my laptop.
Both running Windows 7 and Java JDK/JRE 6 update 20
I hope someone can help me ;)
Below the code that gives the error:
import java.io.File;
import javax.swing.JFileChooser;
public class NewMain {
    public static void main(String[] args) {
        JFileChooser fc = new JFileChooser();
        fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
        fc.showOpenDialog(fc);
        File folder = new File(fc.getSelectedFile().toString());
        File[] listOfFiles = folder.listFiles();
        for (int i = 0; i < listOfFiles.length; i++) {
            System.out.println(listOfFiles.getName());

Answer 1

wastrel wrote:
Still I think this line looks strange,
fc.showOpenDialog(fc);
This method should be called with the parent Component and it doesn't seem right to use the JFileChooser object as its own parent. I suggest you try this instead,
fc.showOpenDialog(null);
With a little luck the bug is associated with the case where a parent Component is specified.Not a chance. As the JFileChooser hasn't been added to a Window, the call to JOptionPane.getWindowForComponent(parent) in JFileChooser.createDialog(Component parent) returns SwingUtilities.getSharedOwnerFrame(). The same results from passing null instead of fc. See the sources for JFileChooser and JOptionPane.
That said, it's certainly bad programming practice to pass as the parent parameter any reference that cannot possibly be used as a parent for the resulting dialog.
db