Java IO.pdf - Nguyen Dang Binh

}
}
Java I/O
if (result == JFileChooser.APPROVE_OPTION) {
try {
File f = fc.getSelectedFile();
if (f != null) { // Make sure the user didn't choose a directory.
FileInputStream fin = new FileInputStream(f);
StreamCopier.copy(fin, System.out);
fin.close();
}
}
catch (IOException e) {System.err.println(e);}
}
// Work around annoying AWT non-daemon thread bug.
System.exit(0);
This program is shorter and simpler than Example 13.1. It's also more reliable across different
platforms. The only downside is that it's noticeably slower to start up. However, that's because
it must load the entire Swing package. A program that's using many Swing classes won't have
to pay that penalty more than once. The only other disadvantage is that standard file extenders
like Action Files or Super Boomerang won't notice a file chooser, whereas they will work
inside a file dialog brought up by a Java program.
13.2.4 Programmatically Manipulating the JFileChooser
The JFileChooser class includes several methods to specify which files and directories are
selected and displayed when the chooser is shown. These include:
public void changeToParentDirectory()
public void rescanCurrentDirectory()
public void ensureFileIsVisible(File f)
The changeToParentDirectory() method simply displays the parent directory of the
directory currently displayed; that is, it moves one level up in the directory hierarchy. The
rescanCurrentDirectory() method refreshes the list of files shown. Use it when you have
reason to believe a file may have been added to or deleted from the directory.
ensureFileIsVisible() scrolls the list up or down until the specified file is shown.
Three methods allow you to specify which directory and file are selected in the file chooser:
public void setSelectedFile(File selectedFile)
public void setSelectedFiles(File[] selectedFiles)
public void setCurrentDirectory(File dir)
You can use these to point the user at a particular file. For instance, a Java source code editor
might like to set the filename to the title of the class being edited plus the customary .java
extension. Another common example: if the user opens a file, edits it, then selects Save As...
from the File menu, it's customary to bring up the save dialog with the previous location of
the file already selected. The user can change this if they like.
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