10.Callable与Future的应用

 1 import java.util.Random;
 2 import java.util.concurrent.Callable;
 3 import java.util.concurrent.CompletionService;
 4 import java.util.concurrent.ExecutionException;
 5 import java.util.concurrent.ExecutorCompletionService;
 6 import java.util.concurrent.ExecutorService;
 7 import java.util.concurrent.Executors;
 8 import java.util.concurrent.Future;
 9 
10 /**
11  * Callable与Future的应用
12  * Future取得的结果类型和Callable返回的结果类型必须一致，这是通过泛型来实现。
13  * Callable要采用ExecutorService的submit方法提交，返回的future对象可以取消任务。
14  * CompletionService用于提交一组Callable任务，其take方法返回已完成的一个Callable任务对应的Future对象。
15  * @author LiTaiQing
16  *
17  */
18 public class CallableAndFuture {
19     
20     public static void main(String[] args) {
21         
22         ExecutorService threadPool = Executors.newSingleThreadExecutor();
23         Future<String> future = 
24         //有返回结果时用submit
25         threadPool.submit(new Callable<String>(){
26             @Override
27             public String call() throws Exception {
28                 return "Hello";
29             }
30             
31         });
32         
33         System.out.println("等待结果");
34         try {
35             System.out.println("拿到结果" + future.get());
36         } catch (InterruptedException e) {
37             e.printStackTrace();
38         } catch (ExecutionException e) {
39             e.printStackTrace();
40         }
41         
42         ExecutorService threadPool2 = Executors.newFixedThreadPool(10);
43         CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2);
44         for(int i = 1; i < 10; i++){
45             final int seq = i;
46             completionService.submit(new Callable<Integer>(){
47                 @Override
48                 public Integer call() throws Exception {
49                     Thread.sleep(new Random().nextInt(5000));
50                     return seq;
51                 }
52                 
53             });
54         }
55         
56         for(int i = 0 ; i < 10; i++){
57             try {
58                 System.out.println(completionService.take().get());
59             } catch (InterruptedException e) {
60                 e.printStackTrace();
61             } catch (ExecutionException e) {
62                 e.printStackTrace();
63             };
64         }
65         
66     }
67     
68 }