Synchronization of a variable during polling

[Fubarable]

I need help with concurrency, one of my weaknesses.

I have a program that is continually polling the screen to see if a program I am trying to control has changed signficantly. It compares the current image to a reference image. There are times when I want to change the reference image to the current image, and so I have given the polling class a volatile private boolean called reset plus a synchronized setter method:

   private volatile boolean reset = false;


   public synchronized void setReset(boolean reset) {
      this.reset = reset;
   }

I don't want an outside class calling setReset when the image is being reset, so in a bit of code that is being called repeatedly, I have a synchronized block:

   public void startPolling() {
      final Runnable myRunnable = new Runnable() {
         public void run() {

            // bunch of code deleted

            // but this is where I compare the currently obtained image
            // with the reference image

            synchronized (this) {
               if (reset) {
                  referenceImgDataVector = currentImgDataVector;
                  reset = false; // should I call the setter here?
                  // setReset(false); // like so?
               }
            }

         }
      };
      long initialDelay = 0;
      long period = freq;
      TimeUnit timeUnit = TimeUnit.MILLISECONDS;
      scheduler = Executors.newScheduledThreadPool(1);
      futureHandler = scheduler.scheduleAtFixedRate(myRunnable, initialDelay,
            period, timeUnit);
   }

There will only be one instance of the above class, and there will only be one outside object ever calling reset. Will this work for me?
And should I call the setter in the synchronized block?

If an SSCCE is desired, I'd be happy to make one.

Thanks in advance!

[Norm]

Can you post a SSCCE? I need something to get my teeth into.

[Fubarable]

Can you post a SSCCE? I need something to get my teeth into.

Thanks Norm. I'm going to try to produce one tomorrow.

[kjkrum]

One problem I can see: synchronized(this) in the Runnable synchronizes on the anonymous Runnable instance, not the enclosing class instance. It should be synchronized(EnclosingClassName.this).

If the reset variable in the enclosing class is not hidden by a local variable or member of the Runnable, then once you fix the synchronization you can just put reset = false in the synchronized block. (If it is hidden, you could put EnclosingClassName.this.reset = false.)