ThreadPoolExecutor backport

Hello
I'm using the backport to java 1.4 of Doug Lea's java.util.concurrent
package. In the doc for ThreadPoolExecutor, there is a snipped of code
to build a pausable thread pool executor. The snipped is below.
Q: Why does the boolean flag isPaused need not be volatile?
As I see it, it will be polled and set by different threads and
nothing guarantees a memory barrier.
Q2: Does it make a difference if you are in the 1.4 or java 5 memory
model?
Thanks for your comments. Phil

--- Code from JavaDoc ---

class PausableThreadPoolExecutor extends ThreadPoolExecutor {
   private boolean isPaused;
   private ReentrantLock pauseLock = new ReentrantLock();
   private Condition unpaused = pauseLock.newCondition();

   public PausableThreadPoolExecutor(...) { super(...);

   protected void beforeExecute(Thread t, Runnable r) {
     super.beforeExecute(t, r);
     pauseLock.lock();
     try {
       while (isPaused) unpaused.await();
     } catch (InterruptedException ie) {
       t.interrupt();
     } finally {
       pauseLock.unlock();
     }
   }

   public void pause() {
     pauseLock.lock();
     try {
       isPaused = true;
     } finally {
       pauseLock.unlock();
     }
   }

   public void resume() {
     pauseLock.lock();
     try {
       isPaused = false;
       unpaused.signalAll();
     } finally {
       pauseLock.unlock();
     }
   }
 }}