Mythread m =new Mythread();
        FutureTask futureTask=new FutureTask(m);
        new Thread(futureTask,"A").start();
    //new Thread(futureTask,"B").start();  --结果会被缓存 效率高
        Object o=futureTask.get();  //这个get方法可能会导致阻塞 ！把他放在最后
        System.out.println(o);
    }
}

class Mythread implements Callable<String> {  

    @Override
    public String call() throws Exception {
        System.out.println("call");
        return "1024";
    }
}

细节
1.有缓存
2.结果可能需要等待,会阻塞！