Java CompletableFuture（1）

 private Long longTimeWork() {
        try {
            //模拟耗时操作，特意阻塞5秒。
            TimeUnit.SECONDS.sleep(5);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        return System.currentTimeMillis();
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        System.out.println("时间1:" + System.currentTimeMillis());
        CompletableFuture<Long> future = CompletableFuture.supplyAsync(() -> longTimeWork());
        System.out.println("时间2:" + System.currentTimeMillis());
        Future<Long> f = future.whenComplete((v, a) -> {
            System.out.println("时间3:" + System.currentTimeMillis());
            System.out.println("v: " + v);
            System.out.println("a: " + a);
            System.out.println("时间4:" + System.currentTimeMillis());
        });
        System.out.println("时间5:" + System.currentTimeMillis());
    }

输出：

06-12 16:28:23.157 4686-4686/zhangphil.test I/System.out: 时间1:1528792103157
06-12 16:28:23.161 4686-4686/zhangphil.test I/System.out: 时间2:1528792103161
06-12 16:28:23.162 4686-4686/zhangphil.test I/System.out: 时间5:1528792103162
06-12 16:28:28.164 4686-4710/zhangphil.test I/System.out: 时间3:1528792108164
06-12 16:28:28.165 4686-4710/zhangphil.test I/System.out: v: 1528792108164
    a: null
    时间4:1528792108165