Threaded File Checker

[Mark Mero]

I am looking to create a file checker that will check the availability of multiple files. I want this to be threaded so that multiple files can be checked for at the same time.

[Stan James]

To run a task on multiple threads, encapsulate the task code in its own class. Make the task class implement Runnable and put the task code in the run() method. Then you can do something like this:

for each file
   Task t = new Task(filename);
   taskList.add(t);
   new Thread(t).start();
next
 
for each Task in tasklist
   Task t = next task
   join(t);
   results.add(t.getResult());
next

I'll let you work out Task ... the run() method contains the file check code and saves the result in a member variable.

That's real sketchy ... is it enough to go on?

[Peter Chase]

Originally posted by Mark Mero:
I am looking to create a file checker that will check the availability of multiple files. I want this to be threaded so that multiple files can be checked for at the same time.

Forgive me if you have already looked into this issue, but it seems to me that this might not be a good application for multi-threading. If all the files are on the same file system, then checking for lots of files "all at once" may not achieve improved performance.

[Mark Mero]

Sorry if i didn't explain myself very well.

The thread will target a file checking class that will loop through the file definitions until all files have been received.

[Stan James]

The logic I showed above would do the trick if each task looped inside its run method until the file existed. But it would be overkill. You don't need a thread per file, just one thread for the checker. Here's a possibility not quite in Java ...

class Checker implements Runnable
{
   Collection files
 
   public Checker(Collection files)
   {
      this.files = files
   }
 
   public void run()
   {
      while files size > 0
         sleep a while
         get an iterator
         while iterator has next
            filename = next
            if new File(filename) exists
               iterator.remove()
         end while has next
      end while size > 0
   }
}

At any moment the collection contains a list of files not yet found if anybody else is interested. You might have to synchronize any get on the remaining list.