Java IO.pdf - Nguyen Dang Binh

Java I/O
assume the array returned by listRoots() necessarily has any members! null is returned if
the list can't be determined at all. This is not the same thing as a zero-length array.
The list of roots may or may not contain drives that are mounted over the network. If the drive
is mounted in such a fashion that it pretends to be a local drive, it probably will be in the list.
If the filesystem does not look like a local drive, it probably won't appear in the list. For
instance, on Windows, network drives mapped to letters appear, but drives with UNC
pathnames do not. Example 12.1 is a very simple program to list the roots and print them.
Example 12.1. RootLister
import java.io.*;
public class RootLister {
}
public static void main(String[] args) {
}
File[] roots = File.listRoots();
for (int i = 0; i < roots.length; i++) {
System.out.println(roots[i]);
}
Here's the output produced by RootLister on my Windows NT system. A: is the floppy
drive. This system doesn't have a second floppy, which would normally be B:. C:, D:, E:, and
F: are all partitions of the primary hard drive that appear to be separate drives. G: is the Zip
drive, and H: is the CD-ROM. I: is a Macintosh drive mounted over the LAN.
D:\JAVA\ioexamples\12>java RootLister
A:\
C:\
D:\
E:\
F:\
G:\
H:\
I:\
The output on Unix is much simpler and is virtually guaranteed to look like this:
% java RootLister
/
Since Java 2 isn't available for the Mac at the time of this writing, I can only speculate about
what the output is likely to be on that platform. However, it will probably look something like
this:
Macintosh HD
System 8
Drive D
Drive F
The exact names would depend on the names the user gave to the individual hard drives and
network servers.
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