java多线程 Future 模式

public static void main(String[] args)throws Exception{

    Callable c1 = new Callable() {
        @Override
        public Object call() throws Exception {
            System.out.println("task1 start");
            Thread.sleep(2000);
            System.out.println("task1 end");
            return "完成 任务1 ";
        }
    };
    FutureTask<String> futureTask = new FutureTask<String>(c1);
    new Thread(futureTask).start();

    Callable c2= new Callable() {
        @Override
        public Object call() throws Exception {
            System.out.println("task2 start");
            Thread.sleep(3000);
            System.out.println("task2 end");
            return "完成 任务2";
        }
    };

    FutureTask futureTask2 = new FutureTask(c2);
    new Thread(futureTask2).start();

    System.out.println(futureTask.get());
    System.out.println(futureTask2.get());
}

运行结果：

task1 start
task2 start
task1 end
完成 任务1 
task2 end
完成 任务2

可以看到task1和task2是同时运行的，task2不用等待task1完成后才执行，但是又能确保 先用task1的结果，后用task2的结果。

利用线程池来执行：

  //声明固定线程数为5的线程池
   static ExecutorService mService = Executors.newFixedThreadPool(5);

/**
     * future模式 Future
     */
    public static void testFuture1() throws ExecutionException, InterruptedException {
        Future<String> future = mService.submit(()->{
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "有返回值 运行结束";
        });
        System.out.println("future is Down1:"+future.isDone());
        System.out.println(future.get());
        System.out.println("future is Down2:"+future.isDone());
    }

  /**
     * FutureTask
     */
    public static void testFuture2() throws ExecutionException, InterruptedException {
        FutureTask<String> futureTask = new FutureTask<>(()->{
            Thread.sleep(3000);
            return "运行成功";
        });
        mService.execute(futureTask);
        System.out.println("futureTask is Down1:"+futureTask.isDone());
        System.out.println(futureTask.get());
        System.out.println("futureTask is Down2:"+futureTask.isDone());
    }

上诉用线程池执行了两种方式写的Future模式