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FileLister.javaAPI DocExample8505Sat Jun 02 02:41:14 BST 2001None

FileLister

public class FileLister extends CloseableFrame implements ActionListener, ItemListener
This class creates and displays a window containing a list of files and sub-directories in a specified directory. Clicking on an entry in the list displays more information about it. Double-clicking on an entry displays it, if a file, or lists it if a directory. An optionally-specified FilenameFilter filters the displayed list.

Fields Summary
private List
list
private TextField
details
private Panel
buttons
private Button
up
private Button
close
private File
currentDir
private FilenameFilter
filter
private String[]
files
private DateFormat
dateFormatter
Constructors Summary
public FileLister(String directory, FilenameFilter filter)
Constructor: create the GUI, and list the initial directory.

  
                
        
    super("File Lister");              // Create the window
    this.filter = filter;              // Save the filter, if any
    
    list = new List(12, false);        // Set up the list
    list.setFont(new Font("MonoSpaced", Font.PLAIN, 14));
    list.addActionListener(this);
    list.addItemListener(this);
    
    details = new TextField();         // Set up the details area
    details.setFont(new Font("MonoSpaced", Font.PLAIN, 12));
    details.setEditable(false);

    buttons = new Panel();             // Set up the button box
    buttons.setLayout(new FlowLayout(FlowLayout.RIGHT, 15, 5));
    buttons.setFont(new Font("SansSerif", Font.BOLD, 14));

    up = new Button("Up a Directory"); // Set up the two buttons
    close = new Button("Close");
    up.addActionListener(this);
    close.addActionListener(this);

    buttons.add(up);                   // Add buttons to button box
    buttons.add(close);
    
    this.add(list, "Center");          // Add stuff to the window
    this.add(details, "North");
    this.add(buttons, "South");
    this.setSize(500, 350);
    
    listDirectory(directory);          // And now list the initial directory.
  
Methods Summary
public voidactionPerformed(java.awt.event.ActionEvent e)
This ActionListener method is invoked when the user double-clicks on an entry or clicks on one of the buttons. If they double-click on a file, create a FileViewer to display that file. If they double-click on a directory, call the listDirectory() method to display that directory

    if (e.getSource() == close) this.dispose();
    else if (e.getSource() == up) { up(); }
    else if (e.getSource() == list) {  // Double click on an item
      int i = list.getSelectedIndex(); // Check which item
      if (i == 0) up();                // Handle first Up To Parent item
      else {                           // Otherwise, get filename
        String name = files[i-1]; 
        File f = new File(currentDir, name);    // Convert to a File
        String fullname = f.getAbsolutePath();
        if (f.isDirectory()) listDirectory(fullname);  // List a directory
        else new FileViewer(fullname).show();          // or display a file
      }
    }
  
public voiditemStateChanged(java.awt.event.ItemEvent e)
This ItemListener method uses various File methods to obtain information about a file or directory. Then it displays that info in the details box.

    int i = list.getSelectedIndex() - 1;      // minus 1 for Up To Parent entry
    if (i < 0) return;
    String filename = files[i];               // Get the selected entry 
    File f = new File(currentDir, filename);  // Convert to a File
    if (!f.exists())                          // Confirm that it exists
      throw new IllegalArgumentException("FileLister: " +
                                         "no such file or directory");

    // Get the details about the file or directory, concatenate to a string
    String info = filename;
    if (f.isDirectory()) info += File.separator;
    info += " " + f.length() + " bytes ";
    info += dateFormatter.format(new java.util.Date(f.lastModified()));
    if (f.canRead()) info += " Read";
    if (f.canWrite()) info += " Write";

    // And display the details string
    details.setText(info);
  
public voidlistDirectory(java.lang.String directory)
This method uses the list() method to get all entries in a directory and then displays them in the List component.

    // Convert the string to a File object, and check that the dir exists
    File dir = new File(directory);
    if (!dir.isDirectory()) 
      throw new IllegalArgumentException("FileLister: no such directory");

    // Get the (filtered) directory entries
    files = dir.list(filter);        
    // And sort them.
    Sorter.sort(files);

    // Remove any old entries in the list, and add the new ones
    list.removeAll();
    list.addItem("[Up to Parent Directory]");  // A special case entry
    for(int i = 0; i < files.length; i++) list.addItem(files[i]);
    
    // Display directory name in window titlebar and in the details box
    this.setTitle(directory);
    details.setText(directory);

    // Remember this directory for later.
    currentDir = dir;
  
public static voidmain(java.lang.String[] args)
A main() method so FileLister can be run standalone. Parse command line arguments and create the FileLister object. If an extension is specified, create a FilenameFilter for it. If no directory is specified, use the current directory.

    FileLister f;
    FilenameFilter filter = null;  // The filter, if any
    String directory = null;       // The specified dir, or the current dir
    
    // Loop through args array, parsing arguments
    for(int i = 0; i < args.length; i++) {
      if (args[i].equals("-e")) {
        if (++i >= args.length) usage();
        final String suffix = args[i];  // final for use in anon. class below

        // This class is a simple FilenameFilter.  It defines the
        // accept() method required to determine whether a specified
        // file should be listed.  A file will be listed if its name
        // ends with the specified extension, or if it is a directory.
        filter = new FilenameFilter() {
          public boolean accept(File dir, String name) {
            if (name.endsWith(suffix)) return true;
            else return (new File(dir, name)).isDirectory();
          }
        };
      }
      else {
        if (directory != null) usage();  // If dir already specified, fail.
        else directory = args[i];
      }
    }
    
    // if no directory specified, use the current directoy
    if (directory == null) directory = System.getProperty("user.dir");
    // Create the FileLister object, with directory and filter specified.
    f = new FileLister(directory, filter);
    // Arrange for the application to exit when the FileLister window closes
    f.addWindowListener(new WindowAdapter() {
      public void windowClosed(WindowEvent e) { System.exit(0); }
    });
    // And pop up the FileLister.
    f.show();
  
protected voidup()
A convenience method to display the contents of the parent directory

    String parent = currentDir.getParent();
    if (parent == null) return;
    listDirectory(parent);
  
public static voidusage()
A convenience method used by main()

    System.out.println("Usage: java FileLister [directory_name] " + 
                       "[-e file_extension]");
    System.exit(0);