准备面试总结下
1.CompletableFuture
static ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(10, 20, 1000L, TimeUnit.MICROSECONDS, new ArrayBlockingQueue<>(100));public static void main(String[] args) throws ExecutionException, InterruptedException {CompletableFuture<Integer> task1 = CompletableFuture.supplyAsync(() -> {try {System.out.println("task1");Thread.sleep(1000);} catch (InterruptedException e) {throw new RuntimeException(e);}return 1000;}, poolExecutor);CompletableFuture<Integer> task2 = CompletableFuture.supplyAsync(() -> {try {System.out.println("task2");Thread.sleep(2000);} catch (InterruptedException e) {throw new RuntimeException(e);}return 2000;}, poolExecutor);CompletableFuture<Integer> task3 = CompletableFuture.supplyAsync(() -> {try {System.out.println("task3");Thread.sleep(10000);} catch (InterruptedException e) {throw new RuntimeException(e);}return 5000;}, poolExecutor);Integer result1 = task1.get();System.out.println(result1);Integer result2 = task2.get();System.out.println(result2);Integer result3 = task3.get();System.out.println(result3);CompletableFuture<Void> voidCompletableFuture = CompletableFuture.allOf(task1, task2, task3);poolExecutor.shutdown();System.out.println("执行完毕");}2.CoutDownLatch
static HashMap<String, Integer> map = new HashMap<String, Integer>();public static void main(String[] args) throws InterruptedException, ExecutionException {ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(10, 20, 1000L, TimeUnit.MICROSECONDS, new ArrayBlockingQueue<>(100));CountDownLatch countDownLatch = new CountDownLatch(3);Future<Integer> task1 = poolExecutor.submit(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {System.out.println("任务1");Thread.sleep(1000);System.out.println("任务1结束");countDownLatch.countDown();return 1000;}});Future<Integer> task2 = poolExecutor.submit(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {System.out.println("任务2");Thread.sleep(500);System.out.println("任务2结束");countDownLatch.countDown();return 500;}});Future<Integer> task3 = poolExecutor.submit(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {System.out.println("任务3");Thread.sleep(2000);System.out.println("任务3结束");countDownLatch.countDown();return 2000;}});map.put("task1", task1.get());map.put("task2", task1.get());map.put("task3", task1.get());System.out.println("线程跑完了");countDownLatch.await();System.out.println("---------------任务执行结束-------------");poolExecutor.shutdown();}3.阻塞获取异步调用结果
public static void main(String[] args) throws ExecutionException, InterruptedException {ExecutorService executorService = Executors.newFixedThreadPool(3);Future<String> submit = executorService.submit(new Callable<String>() {@Overridepublic String call() throws Exception {Thread.sleep(1000);return "Its done";}});while (true){if (submit.isDone()){System.out.println(submit.get());break;}System.out.println(submit.isDone());}}4.除了上面两个方法 还有 CyclicBarrier，Semaphore也都可以实现，可以自己尝试下
