How can I get a list of all mounted filesystems in Java on Unix?

Question

I'm running Java on a Unix platform. How can I get a list of all mounted filesystems via the Java 1.6 API?

I've tried File.listRoots() but that returns a single filesystem (that is, /). If I use df -h I see more than that:

Filesystem      Size   Used  Avail Capacity   iused     ifree %iused  Mounted on
/dev/disk0s2   931Gi  843Gi   87Gi    91% 221142498  22838244   91%   /
devfs          187Ki  187Ki    0Bi   100%       646         0  100%   /dev
map -hosts       0Bi    0Bi    0Bi   100%         0         0  100%   /net
map auto_home    0Bi    0Bi    0Bi   100%         0         0  100%   /home
/dev/disk1s2   1.8Ti  926Gi  937Gi    50% 242689949 245596503   50%   /Volumes/MyBook
/dev/disk2     1.0Gi  125Mi  875Mi    13%     32014    223984   13%   /Volumes/Google Earth

I would expect to see /home as well (at a minimum).

Answer 1

In Java7+ you can use nio

import java.io.IOException;
import java.nio.file.FileStore;
import java.nio.file.FileSystems;

public class ListMountedVolumesWithNio {
   public static void main(String[] args) throws IOException {
      for (FileStore store : FileSystems.getDefault().getFileStores()) {
         long total = store.getTotalSpace() / 1024;
         long used = (store.getTotalSpace() - store.getUnallocatedSpace()) / 1024;
         long avail = store.getUsableSpace() / 1024;
         System.out.format("%-20s %12d %12d %12d%n", store, total, used, avail);
      }
   }
}

Answer 2

Java doesn't provide any access to mount points. You have to run system command mount via Runtime.exec() and parse its output. Either that, or parse the contents of /etc/mtab.