FutureTask.cancel() - can anyone explain the mechanism?

Hi,

I have a class which implements Callable<Integer> which is submitted
to an ExecutorService

two methods of interest are as follows

// Called from producer thread.
public void addMessage(final String message) {

   try {
      blockingQueue.put(message);
   }
   catch (InterruptedException ie) {
      // Log exception
   }
}

// Implement Callable<Integer>
// Consume messages from blocking queue
public Integer call() {

   try {
      while (true) {
         final String message = blockingQueue.take();
      }
   }
   catch (Throwable t) {
      // log Throwable
   }
   finally {
      // Log that Thread has been cancelled/stopped
   }

   return 0;
}

When I submit the Callable to ExecutorService I receive a Future of
concrete class FutureTask.

If I invoke futureTask.cancel() I can see that I jump straight to the
finally clause of my call() method. No exceptions appear to be thrown.

Could someone explain to me

1. Why this happens.
2. If this is a safe mechanism for stopping my consumer thread.
3. If this is safe can I submit a Runnable instead of a callable and
safely cancel the Thread this way?

Many thanks for any help.