| // com.google.common.util.concurrent.MoreExecutors#shutdownAndAwaitTermination
public static boolean shutdownAndAwaitTermination(
ExecutorService service, long timeout, TimeUnit unit) {
// 把阻塞时间平分
long halfTimeoutNanos = unit.toNanos(timeout) / 2;
// Disable new tasks from being submitted
// 这一步是必做的，保证线程池不再接受新的任务
service.shutdown();
try {
// Wait for half the duration of the timeout for existing tasks to terminate
// 先最多等设置的阻塞时间的一半时间
if (!service.awaitTermination(halfTimeoutNanos, TimeUnit.NANOSECONDS)) {
// Cancel currently executing tasks
// 考虑到有些任务可能处于阻塞状态，直接 shutdownNow，会中断执行的任务
service.shutdownNow();
// Wait the other half of the timeout for tasks to respond to being cancelled
service.awaitTermination(halfTimeoutNanos, TimeUnit.NANOSECONDS);
}
} catch (InterruptedException ie) {
// Preserve interrupt status
Thread.currentThread().interrupt();
// (Re-)Cancel if current thread also interrupted
service.shutdownNow();
}
return service.isTerminated();
}
| 
