CompletableFuture 使用

说明 

　　CompletableFuture是java8 中用来并发编程使用的，非常方便，功能上可以替换Semaphore的使用

 1 import java.util.Random;
 2 import java.util.concurrent.*;
 3 
 4 
 5 public class FutureTest {
 6 
 7     // 线程池
 8     private static ExecutorService executorService = Executors.newFixedThreadPool(3);
 9 
10     public static void main(String[] args) {
11         try {
12             StringBuilder sb = new StringBuilder();
13 
14             // 正常操作
15             CompletableFuture<String> c1 = CompletableFuture.supplyAsync(() -> {
16                 sleep();
17                 return "1";
18             }, executorService).thenApply(s -> {
19                 sb.append(s);
20                 return s;
21             });
22 
23 
24             // 异常处理
25             CompletableFuture<String> c2 = CompletableFuture.supplyAsync(() -> {
26                 sleep();
27                 throw new RuntimeException("exception");
28             }, executorService).exceptionally(exception -> "exception_2").thenApply(obj -> {
29                 sb.append(obj);
30                 return obj.toString();
31             });
32 
33             // 未报异常
34             CompletableFuture<String> c3 = CompletableFuture.supplyAsync(() -> {
35                 sleep();
36                 return "3";
37             }, executorService).exceptionally(s -> "exception").thenApply(obj -> {
38                 sb.append(obj);
39                 return obj;
40             });
41 
42 
43             long start = System.currentTimeMillis();
44             System.out.println("start:" + start);
45             CompletableFuture<Void> voidCompletableFuture = CompletableFuture.allOf(c1, c2, c3);
46             try {
47                 //所有线程只等待1s，会有超时的，所以会报timeoutException,catch 住之后，会有上部分数据没有被处理(sb.append(xxx))
48                 voidCompletableFuture.get(1, TimeUnit.SECONDS);
49             } catch (Exception e) {
50                 e.printStackTrace();
51             }
52 
53 
54             long complete = System.currentTimeMillis();
55             System.out.println("complete:" + complete);
56             System.out.println("cost:" + (complete - start));
57             // 如果 调用 get方法，则会等待返回值,那么所有的sb.append 都会被处理
58 //        System.out.println(c1.get());
59 //        System.out.println(c2.get());
60 //        System.out.println(c3.get());
61             System.out.println(sb);
62             long finish = System.currentTimeMillis();
63             System.out.println("finish:" + finish);
64             System.out.println("cost:" + (finish - start));
65 
66         } finally {
67             executorService.shutdown();
68         }
69 
70     }
71 
72     private static void sleep() {
73         try {
74             Thread.sleep(new Random().nextInt(2000));
75         } catch (InterruptedException e) {
76             e.printStackTrace();
77         }
78     }
79 }