### Question:
ThreadPoolUtils { public static void shutdown(ExecutorService executorService) { doShutdown(executorService, 0); }  static void shutdown(ExecutorService executorService); static List<Runnable> shutdownNow(ExecutorService executorService); static void shutdownGraceful(ExecutorService executorService); static void shutdownGraceful(ExecutorService executorService, long shutdownAwaitTermination); static boolean awaitTermination(ExecutorService executorService, long shutdownAwaitTermination); static final long DEFAULT_SHUTDOWN_AWAIT_TERMINATION; }### Answer:
@Test(timeout=10000) public void testShutdown() throws Exception { ExecutorService service = Executors.newSingleThreadExecutor(); ThreadPoolUtils.shutdown(service); assertTrue(service.isShutdown()); }
@Test(timeout=10000) public void testShutdownNullService() throws Exception { ThreadPoolUtils.shutdown(null); }