多线程-Callable

 

1.FutureTask是Runnable接口的实现类，刚好构造器方法可以传入Callable.,然后就可以通过

new Thread(new FutureTask(new Callable())).start()类似方法创建线程执行，习惯使用lambda表达式。

 

 

代码如下:

class MyThread1 implements  Runnable {

    @Override
    public void run() {

    }
}

class MyThread2 implements Callable<Integer> {

    @Override
    public Integer call() throws Exception {
        System.out.println(Thread.currentThread().getName()+"  come in callable");
        return 200;
    }
}


public class CallableTest {
    public static void main(String[ ]args) throws ExecutionException, InterruptedException {

      //  FutureTask<Integer> futureTask1 = new FutureTask<>(new MyThread2());
        FutureTask<Integer> futureTask2 = new FutureTask<>(() -> {
            System.out.println(Thread.currentThread().getName()+"  come in callable");
            return 1000;
        });

       // new Thread(new MyThread1(),"t1").start();
       // new Thread(futureTask1,"t2").start();

        new Thread(futureTask2,"t3").start();
        while (!futureTask2.isDone()) {
            System.out.println("wait-----");
        }

        //  System.out.println(futureTask1.get());
        System.out.println(futureTask2.get());
        System.out.println(futureTask2.get());
        System.out.println(Thread.currentThread().getName()+ " 执行完毕");

    }
}

结果如下:

 

 

 

总结: 

注意，当第二次调用futureTask2.get()方法时，会直接返回结果不会再等待做运算，要跟第一个做下区分