Java IO.pdf - Nguyen Dang Binh

Figure 13.2. Motif standard Open dialog
Java I/O
FileDialog is a subclass of java.awt.Dialog that represents the native save and open
dialog boxes:
public class FileDialog extends Dialog
A file dialog is almost completely implemented by a native peer. Your program doesn't add
components to a file dialog or handle user interaction with event listeners. It just displays the
dialog and retrieves the name and directory of the file the user chose after the dialog is
dismissed.
Since applets normally can't read or write files, file dialogs are primarily useful only in
applications. Nonetheless, there is no specific security manager check to see whether file
dialogs are allowed. Sun's applet viewer, HotJava, and some recent versions of Netscape
Navigator do allow untrusted applets to display file dialogs, retrieve the name and path of the
file selected, and send that information back to the originating host over the network.
Although this is a very minor security hole, since it only exposes the name and path of a
single file selected by the user, it's still on the worrisome side for the paranoid. Internet
Explorer 4.0 and Navigator 4.0.3 and earlier do not allow applets to display file dialogs.
Certainly, you can't count on being allowed to use a file dialog in an applet, nor can you be
guaranteed that it isn't allowed either.
To ask the user to select a file from a file dialog, perform these four steps:
1. Construct a FileDialog object.
2. Set the default directory or file for the dialog (optional).
3. Make the dialog visible.
4. Get the name and directory of the file the user chose.
There is one FileDialog constructor:
public FileDialog(Frame parent, String title, int mode)
The first argument is the parent frame of this file dialog. This will normally be the main
window of the application, the applet's parent, or the frontmost window of the application.
Conversely, you can just create a new frame; you're not required to show the frame if you
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