线程异步的意义和使用

public class ThreadImpl extends Thread {
    @Override
    public void run() {
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        System.out.println(">>>>>>>>>>>>>>>123");
    }
}

public class MyThread {

    public static void main(String[] args) {
        ThreadImpl thread=new ThreadImpl();
        thread.start();
        System.out.println("456");
    }
   
}

 

主线程：456先输出
线程ThreadImpl后输出123，可以看出ThreadImpl并没有阻塞主线程，这样就主线程可以快速执行，子线程继续执行自己的任务。

 

public class MyThread implements Callable {
    @Override
    public Object call() throws InterruptedException {
        Thread.sleep(2000);
        return "123";
    }

    public static void main(String[] args) {
        MyThread call = new MyThread();
        FutureTask futureTask = new FutureTask(call);
        Object o ;

         Thread thread=new Thread(futureTask);
         thread.start();
        try {
            o = futureTask.get();
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } catch (ExecutionException e) {
            throw new RuntimeException(e);
        }
        System.out.println("0000:"+o);
        System.out.println("123456");
    }
}

 

FutureTask具有阻塞作用，上面等两秒，主线程也不会先执行，必须等 futureTask.get()执行后输出123，主线程才输出12346