Java IO.pdf - Nguyen Dang Binh

Java I/O
Example 13.1 is a program that presents an open file dialog to the user, then writes the
contents of the file they selected on System.out. There are many good ways to do this. I
chose to write a static getFile() method that returns a File object; then open and print this
file back in the main() method.
Example 13.1. The FileTyper Program
import java.io.*;
import java.awt.*;
import com.macfaq.io.*;
public class FileChooser {
}
public static void main(String[] args) {
try {
File f = getFile();
if (f == null) return;
FileInputStream fin = new FileInputStream(f);
StreamCopier.copy(fin, System.out);
}
catch (IOException e) {System.err.println(e);}
// Work around annoying AWT non-daemon thread bug.
System.exit(0);
}
public static File getFile() throws IOException {
}
// dummy Frame, never shown
Frame parent = new Frame();
FileDialog fd = new FileDialog(parent, "Please choose a file:",
FileDialog.LOAD);
fd.show();
// Program stops here until user selects a file or cancels.
String dir = fd.getDirectory();
String file = fd.getFile();
// Clean up our windows, they won't be needed again.
parent.dispose();
fd.dispose();
if (dir == null || file == null) { // user cancelled the dialog
return null;
}
return new File(dir, file);
File dialogs only allow the user to select ordinary files, never directories. If you want to ask
users to pick a directory, you have to ask them to choose a file in that directory, then call
getDirectory(). (This workaround fails with empty directories.) Here's an alternative
main() method for the DirList program given in Example 12.5 that uses a file dialog to
select the directory to list rather than command-line arguments:
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