多线程(10) — Callable与Future

作用：获得线程执行完的结果

package ThreadPractice;

import java.util.concurrent.*;

/**
 * Created by qiaorenjie on 2018/3/28.
 */
public class CallableAndFuture {

    public static void main(String[] args) {
         // 1.提交一条线程
         ExecutorService threadPool = Executors.newSingleThreadExecutor();
         Future<String> future =
         threadPool.submit(
                 new Callable<String>() {  // 注意Callable与Future类型必须一致用泛型
                     @Override    // 注意new的是callable
                     public String call() throws Exception { // 不再是runnable中的run而是callable中的call
                         Thread.sleep(2000);
                         return "Hello";
                     }
                 }
         );
        System.out.println("等待结果");
        try {
            System.out.println("拿到结果：" + future.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }

        //2.提交一组线程
        ExecutorService threadPool2 = Executors.newFixedThreadPool(10);
        CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2);
        for (int i = 1; i <= 10; i++) {
            final int seq = i;
            completionService.submit(new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    Thread.sleep(new Random().nextInt(5000));
                    return seq;
                }
            });
        }
        for (int i = 0; i < 10; i++) {
            try {
                System.out.println(completionService.take().get());
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        }

    }
}

=====console======
等待结果
拿到结果：Hello

由此，可以看出Callable接口方法下的call用于写回调结果，new的callable必须要重写call()方法，而call()方法是需要return返回的，在ruturn中写需要回调的信息，再通过Future的get()方法获取到回调的结果数据