Java 串行接口调用优化

准备面试总结下

1.CompletableFuture

java 复制代码

 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

java 复制代码

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>() {
            @Override
            public 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>() {
            @Override
            public 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>() {
            @Override
            public 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

java 复制代码

   public static void main(String[] args) throws ExecutionException, InterruptedException {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        Future<String> submit = executorService.submit(new Callable<String>() {
            @Override
            public 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