Is volatile necessary for variables only accessed inside synchronized block

Question

Hi,
I am using ExecutorService to execute a set of threads. Then the calling thread needs to wait until all of them are done to reuse the thread pool to run another set of threads (so I can't use the ExecutorService.shutdown() to wait for all of the threads at this point). So I write a simple monitor as below to coordinate the threads.
My question is: will it work? someone suggests that it might not work because it will busy spin on the non-volatile int which may or may not be updated with the current value from another thread depending on the whims of the JVM. But I believe that variables accessed inside synchronized blocks should always be current. Can anyone please help me to clarify this? Really appreciate it.
     * Simple synchronization class to allow a thread to wait until a set of threads are done.
     class ThreadCoordinator{
     private int totalActive = 0;
     public synchronized void increment(){
     totalActive++;
     notifyAll();
     public synchronized void decrement(){
     totalActive--;
     notifyAll();
     public synchronized void waitForAll(){
     while(totalActive != 0){
     try{
     wait();
     }catch (InterruptedException e){
     //ignore
     }

Answer 1

Don't do that. Just save the Futures returned by the ExecutorService, and call get() on them all. This will only return when all the tasks have finished.