gistfile1.java

class Santa {
  volatile int reindeers = 0;
  
  // Call this in any old thread when a reindeer arrives
  public synchronized void reindeerArrived() {
    reindeers++;
    notify();
  }
  
  // Returns only when 8 or more reindeer have come in
  public synchronized void awaitAllReindeer() throws InterruptedException {
    while (reindeers < 8) {
      wait();
    }
  }
}

@Test
public void testChristmas() throws InterruptedException {
  final Santa santa = new Santa();
  for (int i = 0; i < 8; i++) {
    final int waitTime = i;
    new Thread(new Runnable() {
      @Override
      public void run() {
        Uninterruptibles.sleepUninterruptibly(waitTime, TimeUnit.SECONDS);
        santa.reindeerArrived();
      }
    }).start();
  }
  
  santa.awaitAllReindeer();
  System.out.println("Here!");
}