线程池之 Callable、Future、FutureTask

　　java线程中的异步和同步，并不是走路，一定要搞清楚。那么join方法嘛，就是异步变同步。线程阻塞，就再楼下一直等着它想要的状态出现喽。直接上代码，先来看Future获取线程执行结果的使用示例：

public class TestCallable {
    public static void main(String[] args) throws Exception {
        ExecutorService executorService = Executors.newCachedThreadPool();
        Task task = new Task();
        Future<Integer> future = executorService.submit(task);
        executorService.shutdown();
        Thread.sleep(3000);
        System.out.println("主线程" + Thread.currentThread().getName() + "正在执行任务");
        System.err.println("任务运行结果：" + future.get());
        System.out.println("所有任务执行完毕");
    }
}

class Task implements Callable<Integer> {
    @Override
    public Integer call() throws InterruptedException {
        System.out.println("子线程" + Thread.currentThread().getName() + "在进行计算：");
        Thread.sleep(4 * 1000);
        int sum = 0;
        for (int i = 0; i < 100; i++) {
            sum += i;
        }
        return sum;
    }
}

　　同样的，FutureTask。http://www.cnblogs.com/dolphin0520/p/3949310.html