FutureTask 不回来结果

FutureTask 不返回结果

ExecutorService pool2 = Executors.newSingleThreadExecutor();
Future result2 = pool2.submit(new FutureTask<String>(
				new Callable<String>() {
					public String call() throws Exception {
						return "TEST";
					}
				}));

String res2 = (String) result2.get();
Thread.sleep(5000);
System.out.println(res2);// 结果怎么是null，我以为是 "TEST" 呢

结果为什么是null呢 
------解决方案--------------------

  public static void main(final String[] args) throws InterruptedException, ExecutionException {
    ExecutorService pool2 = Executors.newSingleThreadExecutor();
    Future<String> result2 = pool2.submit(new Callable<String>() {
      public String call() throws Exception {
        return "TEST";
      }
    });

    Thread.sleep(1000);
    String res2 = result2.get();
    System.out.println(res2);
  }

FutureTask要通过execute方法调用，submit直接传入callable。你这个程序如果用FutureTask来实现要这样：

  public static void main(final String[] args) throws InterruptedException, ExecutionException {
    ExecutorService pool2 = Executors.newSingleThreadExecutor();

    FutureTask<String> task = new FutureTask<>(new Callable<String>() {
      @Override
      public String call() throws Exception {
        return "TEST";
      }
    });
    pool2.execute(task);
    Thread.sleep(100);
    if (task.isDone())