线程池中的线程设置优先级无效

因为优先级是和group有关的，设置单个线程的优先级不能影响group

ExecutorService executorService = Executors.newFixedThreadPool(2);
        for (int i = 0; i <8 ; i++) {
            Thread thread = new Thread(new PriorityThread(),""+i);
            thread.setPriority(4+(int)(Math.random()*(3-0))); // 4-6 随机优先级
//            thread.start();
            executorService.execute(thread);

        }
        executorService.shutdown();