java 多线程返回list对象

 public class Test2 {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newCachedThreadPool();
        Task task = new Task();
        Future<ArrayList> result = executor.submit(task);
        executor.shutdown();

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }

        System.out.println("主线程在执行任务");

        try {
            System.out.println("task运行结果"+result.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

        System.out.println("所有任务执行完毕");
    }
}
class Task implements Callable<ArrayList>{
    @Override
    public ArrayList call() throws Exception {
        System.out.println("子线程在进行计算");
        Thread.sleep(3000);

        return new ArrayList();
    }
}