concurrent包Callable接口

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1.Callable接口与Runnable接口区别：

(1).实现Callable接口和Runnable接口实现类，都是可以被线程执行的任务

(2).Callable接口抛异常，Runnable接口不抛异常

(3).Callable任务运行后，可以获取oncurrent包Future对象，Future对象可以获取任务返回值，Future表示异步计算的结果，提供了检测计算是否完成的方法get(),通过cancel（task）方法，可以取消执行中的任务 Runnable接口不行

(4).类实现Callable接口，要实现Call方法，类实现Runnable接口，要实现run（）方法

public class CallableDemo implements Callable {    private int flag;    public CallableDemo(int flag) {        this.flag = flag;    }    public String call() throws Exception {        if (0 == flag) {            return "0";        } else if (1 == flag) {            Thread.sleep(10000);        }        return "bad parameter";    }    public static void main(String[] args) {        ExecutorService executorService = Executors.newFixedThreadPool(4);        CallableDemo callableDemo1 = new CallableDemo(0);        Future<String> future1 = executorService.submit(callableDemo1);        try {            System.out.println(future1.get());//返回结果，才会执行下面的代码            CallableDemo callableDemo2 = new CallableDemo(1);            Future<String> future2 = executorService.submit(callableDemo2);//等待10s才有数据返回            Thread.sleep(3000);            future2.cancel(true);//中断线程运行            CallableDemo callableDemo3 = new CallableDemo(2);            Future<String> future3 = executorService.submit(callableDemo3);            System.out.println(future3.get());//返回结果，才会执行下面的代码        } catch (InterruptedException e) {            e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.        } catch (ExecutionException e) {            e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.        }    }}

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