public static void main(String[] args) throws Exception {
ExecutorService exec = Executors.newCachedThreadPool();
for (int i = 0; i < 5; i++) {
exec.execute(new Entrance(i));
}
// Run for a while, then stop and collect the data:
TimeUnit.SECONDS.sleep(3);
// Marvin: main线程设置条件，从而使得 Entrance 线程都停下
Entrance.cancel();
// Marvin: exec不再接受新task，运行中的则停下来
exec.shutdown();
if (!exec.awaitTermination(250, TimeUnit.MILLISECONDS))
print("Some tasks were not terminated!");
// Marvin: 这里是在main线程中调用 Entrance.getValue()，这和 Entrance.run()是不同的线程。所以，Entrance.run()中，才同步更新
print("Total: " + Entrance.getTotalCount());
print("Sum of Entrances: " + Entrance.sumEntrances());
}
public static int sumEntrances() {
int sum = 0;
for (Entrance entrance : entrances) sum += entrance.getValue();
return sum;
}