shutdown方法

1.线程池状态变为shutdown

2.不会接收新任务

3.已提交的任务会执行完

4.此方法不会阻塞调用线程执行

ExecutorService executorService = Executors.newFixedThreadPool(2);executorService.submit(() -> {log.debug("task1 running");try {TimeUnit.SECONDS.sleep(1);} catch (InterruptedException e) {e.printStackTrace();}log.debug("task1 finished");});executorService.submit(() -> {log.debug("task2 running");try {TimeUnit.SECONDS.sleep(1);