Accessing a file over the network

Question

Hi ,
I need to access a file for read/write operations. The file may exist or may not on another computer in my network. I use the File class for accessing the file. (File f = new File("\\192.23.23.23\file.txt");
My problem is how can I know if I cannot access the file because I have network issues (e.g. The file exists but the network is down so its not accessible) or because the file really dont exist on the given address.
Since File operations does not throw a specific exception Its hard to know the exact reason for access failure.
Any suggestions ?
Thanks.

Answer 1

Javaist wrote:
Hi ,
I need to access a file for read/write operations. The file may exist or may not on another computer in my network. I use the File class for accessing the file. (File f = new File("\\192.23.23.23\file.txt");
My problem is how can I know if I cannot access the file because I have network issues (e.g. The file exists but the network is down so its not accessible) or because the file really dont exist on the given address.
Since File operations does not throw a specific exception Its hard to know the exact reason for access failure.
Any suggestions ?Here's a complete hack that only uses File that is completely coupled to Windows and the "\\hostname\dir\file..." syntax. This is not a universal solution and strongly urge you not to use it:
public class NetworkFileTest {
   public static void main(String[] args) {
      File file = new File("\\\\myhostname\\tmp\\filethatexists");
      if ( file.exists() ) {
         System.out.println("File exists");
      } else {
         if ( hasPathToHost(file) ) {
            System.out.println("File doesn't exist");
         } else {
            System.out.println("No path to host");
   private static boolean hasPathToHost(File file) {
      if ( file.exists() ) {
         return true;
      } else {
         file = file.getParentFile();
         if ( file != null ) {
            return hasPathToHost(file);
         } else {
            return false;
}This just recursively checks the parent to see if it exists. Once it gets up to the host "directory," it will return false if the network is down, or true otherwise.
Remember that there's absolutely no way to check if a remote file exists if the network is down, short of carrier pigeons. This will just tell you if the file might exist.
Edited by: endasil on 9-Oct-2009 10:43 AM