Is unsynchronized read of integer threadsafe in java?

I see this code quite frequently in some OSS unit tests, but is it thread safe ? Is the while loop guaranteed to see the correct value of invoc ?

If no; nerd points to whoever also knows which CPU architecture this may fail on.

  private int invoc = 0;

  private synchronized void increment() {
    invoc++;
  }

  public void isItThreadSafe() throws InterruptedException {
      for (int i = 0; i < TOTAL_THREADS; i++) {
        new Thread(new Runnable() {
          public void run() {
             // do some stuff
            increment();
          }
        }).start();
      }
      while (invoc != TOTAL_THREADS) {
        Thread.sleep(250);
      }
  }