public class Threads {

   /**
    * sleep等待,單位為毫秒,忽略InterruptedException.
    */
   public static void sleep(long millis) {
      try {
         Thread.sleep(millis);
      } catch (InterruptedException e) {
         // Ignore.
         return;
      }
   }

   /**
    * sleep等待,忽略InterruptedException.
    */
   public static void sleep(long duration, TimeUnit unit) {
 
      try {
         Thread.sleep(unit.toMillis(duration));
      } catch (InterruptedException e) {
         // Ignore.
         return;
      }
   }

   /**
    * 按照ExecutorService JavaDoc示例程式碼編寫的Graceful Shutdown方法.
    * 先使用shutdown, 停止接收新任務並嘗試完成所有已存在任務.
    * 如果超時, 則呼叫shutdownNow, 取消在workQueue中Pending的任務,並中斷所有阻塞函式.
 
    * 如果仍人超時，則強制退出.
    * 另對在shutdown時執行緒本身被呼叫中斷做了處理.
    */
   public static void gracefulShutdown(ExecutorService pool, int shutdownTimeout, int shutdownNowTimeout,
         TimeUnit timeUnit) {
      pool.shutdown(); // Disable new tasks from being submitted
      try {
         // Wait a while for existing tasks to terminate
 
         if (!pool.awaitTermination(shutdownTimeout, timeUnit)) {
            pool.shutdownNow(); // Cancel currently executing tasks
            // Wait a while for tasks to respond to being cancelled
            if (!pool.awaitTermination(shutdownNowTimeout, timeUnit)) {
               System.err.println("Pool did not terminated");
            }
         }
      } catch (InterruptedException ie) {
         // (Re-)Cancel if current thread also interrupted
         pool.shutdownNow();
         // Preserve interrupt status
         Thread.currentThread().interrupt();
      }
   }

   /**
    * 直接呼叫shutdownNow的方法, 有timeout控制.取消在workQueue中Pending的任務,並中斷所有阻塞函式.
    */
   public static void normalShutdown(ExecutorService pool, int timeout, TimeUnit timeUnit) {
      try {
         pool.shutdownNow();
         if (!pool.awaitTermination(timeout, timeUnit)) {
            System.err.println("Pool did not terminated");
         }
      } catch (InterruptedException ie) {
         Thread.currentThread().interrupt();
      }
   }

}