十八、Future 异步回调

1. 没有返回值的异步回调

   public class CompletableFutureDemo {
       public static void main(String[] args) {
   
           //没有返回值的runAsync 异步回调
           CompletableFuture completableFuture =  CompletableFuture.runAsync(()->{
               try {
                   TimeUnit.SECONDS.sleep(2);
                   System.out.println("Future线程执行....");
               } catch (InterruptedException e) {
                   e.printStackTrace();
               }
           });
   
           System.out.println("主线程执行.....");
   
           try {
               //获取异步结果
               System.out.println(completableFuture.get());    //get方法将阻塞
           } catch (InterruptedException e) {
               e.printStackTrace();
           } catch (ExecutionException e) {
               e.printStackTrace();
           }
       }
   }
   

   输出结果为

2. 有返回值的异步回调

   public class CompletableFutureDemo {
       public static void main(String[] args) throws ExecutionException, InterruptedException {
   
           //有返回值的supplyAsync 异步回调
           CompletableFuture<Integer> completableFuture =  CompletableFuture.supplyAsync(()->{
               try {
                   TimeUnit.SECONDS.sleep(2);
                   //  int a = 10/ 0;          //异常测试
                   System.out.println("Future线程执行....");
               } catch (InterruptedException e) {
                   e.printStackTrace();
               }
               return 1024;
           });
   
           System.out.println("主线程执行.....");
   
           System.out.println(completableFuture.whenComplete((t,u)->{
               System.out.println("t->" + t);		//输出正常结果
               System.out.println("u->" + u);		//输出异常信息
           }).exceptionally((e)->{
               System.out.println(e.getMessage());
               return 500;
           }).get());
       }
   }
   

   正常输出

   

   异常输出

   

最后

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